Fully ChargedFind TI’s latest power content at TI.com/powerhousehttps://e2e.ti.com/blogs_/archives/b/fullycharged/atomTelligent Community (Build: 11.1.7.15705)2016-08-22T10:03:00ZExtend battery life with a LDO, a voltage supervisor and a FEThttps://e2e.ti.com/blogs_/archives/b/fullycharged/posts/extend-battery-life-with-a-ldo-a-voltage-supervisor-and-a-fet2017-02-21T19:49:00Z2017-02-21T19:49:00Z<div><b>Other Parts Discussed in Post: </b><a href="https://www.ti.com/product/TPS706" class="internal-link folder product" title="Link to Product Folder" target="_blank">TPS706</a>, <a href="https://www.ti.com/product/TPS3780" class="internal-link folder product" title="Link to Product Folder" target="_blank">TPS3780</a></div><p>Extended battery life is a common design requirement across a variety of applications. Whether it’s for toys or water meters, designers have various techniques at their disposal to improve battery life. In this post, I will illustrate one such technique that involves strategically bypassing a low dropout linear regulator (LDO).</p>
<p><b>Generating the rail</b></p>
<p>Using an LDO is a common way to generate a regulated voltage from the battery. This is especially true with a single-cell lithium-ion (Li-ion) battery that outputs 4.2V when fully charged.</p>
<p>Let’s say that you want to generate 3.3V for a microcontroller (MCU) with a supply voltage range of 3V to 3.6V and you chose the TPS706 to generate this rail. Figure 1 illustrates this circuit.</p>
<p align="center"><a href="/cfs-file/__key/communityserver-blogs-components-weblogfiles/00-00-00-09-40/0474.figure1.PNG"><img src="/resized-image/__size/1230x0/__key/communityserver-blogs-components-weblogfiles/00-00-00-09-40/0474.figure1.PNG" alt=" " /></a></p>
<p align="center"><b>Figure 1: The TPS706 regulating 3.3V from the battery</b></p>
<p>Despite the simplicity of this circuit, it has some limitations. Chief among these is dropout, which will cause the LDO to cease regulation and possibly put the supply voltage of the MCU outside specification.</p>
<p><b>The implications of dropout</b></p>
<p>You can expect the voltage of the Li-ion battery to drop as the battery discharges. Figure 2 shows an example discharge curve.</p>
<p align="center"><a href="/cfs-file/__key/communityserver-blogs-components-weblogfiles/00-00-00-09-40/5265.figure2.jpg"><img src="/resized-image/__size/1230x0/__key/communityserver-blogs-components-weblogfiles/00-00-00-09-40/5265.figure2.jpg" alt=" " /></a></p>
<p align="center"><b>Figure 2: Li-ion battery voltage falling over time</b></p>
<p>This can be troubling when you remember that the LDO risks entering dropout as the input voltage approaches the regulated output voltage. At a certain point, the battery voltage will drop so low that the <a href="http://www.ti.com/product/TPS706" target="_blank">TPS706</a> will no longer be able to regulate 3.3V. Instead, the output voltage will begin to track the battery voltage at a difference equal to the dropout voltage.</p>
<p>The<a href="http://www.ti.com/product/TPS706" target="_blank"> TPS706</a> specifies a typical dropout voltage of 295mV when the output current is 50mA and the output voltage is 3.3V. Thus, it is possible that the LDO could enter dropout once the battery voltage drops below 3.6V. Figure 3 offers an example of such behavior.</p>
<p align="center"><b><a href="/cfs-file/__key/communityserver-blogs-components-weblogfiles/00-00-00-09-40/7331.figure3.PNG"><img src="/resized-image/__size/500x0/__key/communityserver-blogs-components-weblogfiles/00-00-00-09-40/7331.figure3.PNG" alt=" " /></a><br />Figure 3: The TPS706 entering dropout mode</b></p>
<p>As shown, V<sub>OUT</sub> begins to droop once V<sub>IN</sub> falls to around 3.6V. Because the lower end of the MCU supply range is 3V, this is concerning – dropout can cause V<sub>OUT</sub> to fall below 3V very quickly.</p>
<p><b>Avoiding dropout</b></p>
<p>One way to circumvent this issue is to bypass the LDO before or as it enters dropout. Figure 4 illustrates how.</p>
<p align="center"><a href="/cfs-file/__key/communityserver-blogs-components-weblogfiles/00-00-00-09-40/5518.figure4.PNG"><img src="/resized-image/__size/1230x0/__key/communityserver-blogs-components-weblogfiles/00-00-00-09-40/5518.figure4.PNG" alt=" " /></a></p>
<p align="center"><b>Figure 4: Using a P-channel MOSFET to bypass the LDO</b></p>
<p>In this circuit, the TPS3780, a dual-channel voltage detector, monitors the battery voltage via SENSE1. If the battery voltage should fall below 3.4V, OUT1 drives the gate of the P-channel MOSFET low. This enables the current (the blue arrow) to flow through the drain-source terminals of the MOSFET rather than through the input-output terminals of the LDO (the red arrow). Since the MOSFET has lower on-resistance than the LDO, the output voltage will more closely track the input voltage.</p>
<p>SENSE2 monitors the output voltage. Once the output voltage falls below 3V (or the bottom of the supply range of the MCU), OUT2 will assert low. This signal can put the MCU in reset mode.</p>
<p>Figure 5 shows the behavior of the circuit without<i> </i>the aid of the bypass MOSFET.</p>
<p align="center"><a href="/cfs-file/__key/communityserver-blogs-components-weblogfiles/00-00-00-09-40/figure5.jpg"><img src="/resized-image/__size/500x0/__key/communityserver-blogs-components-weblogfiles/00-00-00-09-40/figure5.jpg" alt=" " /></a></p>
<p align="center"><b>Figure 5: A falling input voltage without the bypass MOSFET</b></p>
<p>To simulate a battery, the input voltage is ramped down at a rate of 1V/ms. You can see that once the input voltage hits 3.4V, it takes about 100ms for the output to fall to 3V.</p>
<p>Now, let’s examine the behavior of the circuit that uses the bypass MOSFET, as shown in Figure 6.</p>
<p align="center"><a href="/cfs-file/__key/communityserver-blogs-components-weblogfiles/00-00-00-09-40/figure6.jpg"><img src="/resized-image/__size/500x0/__key/communityserver-blogs-components-weblogfiles/00-00-00-09-40/figure6.jpg" alt=" " /></a></p>
<p align="center"><b>Figure 6: A falling input voltage with the bypass MOSFET</b></p>
<p>Once the input voltage falls below 3.4V, the MOSFET turns on. The output voltage is now equal to the input voltage minus the voltage drop across the MOSFET. As a result, it now takes almost 320ms for the output to reach 3V. By enhancing the PMOS device, the output voltage more closely tracks the input voltage than the LDO does in dropout. In other words, the low on-resistance of the external PMOS effectively allows for a longer battery life.</p>
<p>In reality, the battery voltage will fall at a slower slew rate. Therefore, using a bypass circuit can significantly extend operation time.</p>
<p><b>Current consumption</b></p>
<p>When operating off the battery, you must also consider the current consumption of the circuit. See Table 1.</p>
<div align="center">
<table border="1" cellspacing="0" cellpadding="0">
<tbody>
<tr>
<td width="123" valign="top">
<p align="center"><b>Circuit element</b></p>
</td>
<td width="230" valign="top">
<p align="center"><b>Current (μA)</b></p>
</td>
</tr>
<tr>
<td width="123" valign="top">
<p align="center">TPS706</p>
</td>
<td width="230" valign="top">
<p align="center">1.3 (typ)</p>
</td>
</tr>
<tr>
<td width="123" valign="top">
<p align="center">TPS3780</p>
</td>
<td width="230" valign="top">
<p align="center">2.09 (typ)<sup></sup></p>
</td>
</tr>
<tr>
<td width="123" valign="top">
<p align="center">Resistor networks</p>
</td>
<td width="230" valign="top">
<p align="center">3 (typ)</p>
</td>
</tr>
<tr>
<td width="123" valign="top">
<p align="center">Pull-up resistors</p>
</td>
<td width="230" valign="top">
<p align="center">68 (typ) when the output is low</p>
</td>
</tr>
</tbody>
</table>
</div>
<p align="center"><b>Table 1: Current consumption of various circuit elements</b></p>
<p>Taking this consumption into account is important, as it contributes to the overall discharge of the battery. Fortunately, however, the consumption is very low and the extra circuitry enables sustained use of the battery that outweighs the added current consumption. This is especially true for applications that require higher load currents.</p>
<p><b>Conclusion</b></p>
<p>LDOs are an effective, low current-consumptive method for generating a rail off the battery. However, dropout can cause problems with regulation when the battery voltage starts to droop. Using a MOSFET in conjunction with an LDO helps avoid this issue in order to attain the longest battery life. </p>
<p><strong>Additional resources</strong></p>
<ul>
<li>Read the <a href="http://www.ti.com/lit/an/slva450a/slva450a.pdf">application report</a> for more information on resistor divider current draw and accuracy tradeoffs.</li>
</ul>
<p> </p><div style="clear:both;"></div><img src="https://e2e.ti.com/aggbug?PostID=669430&AppID=940&AppType=Weblog&ContentType=0" width="1" height="1">Aaron Paxtonhttps://e2e.ti.com:443/members/3507752Power your smart lock for five years on one set of batterieshttps://e2e.ti.com/blogs_/archives/b/fullycharged/posts/power-your-smart-lock-for-five-years-on-one-set-of-batteries2017-01-27T23:38:00Z2017-01-27T23:38:00Z<p>Linear regulator, boost (step-up) or buck (step-down) – these are the three power-supply topologies for most smart locks. Which do you choose for your designs? Why does it matter?</p>
<p>The success of any <a href="http://www.ti.com/ww/en/internet_of_things/iot-overview.html" target="_blank">Internet of Things (IoT)</a> device hinges on its ease of use. Primarily, ease of use means the ease of connecting to and controlling the device. But it also refers to the low maintenance of that connected device. How often does it turn off because its batteries need replacing?</p>
<p>A smart lock’s power supply must support a wireless microcontroller (MCU) such as the SimpleLink™ <i>Bluetooth®</i> low energy <a href="http://www.ti.com/product/cc2640r2f" target="_blank">CC2640R2F</a> solution; a motor driver to turn the lock, such as the <a href="http://www.ti.com/product/drv8833" target="_blank">DRV8833</a>; and any other peripherals such as light-emitting diodes (LEDs). Fundamentally, there are three ways to convert the voltage from the batteries to the loads: simply step it down with a low dropout (LDO) linear regulator, step it up with a boost DC/DC converter, or step it down with a buck DC/DC converter.</p>
<p>Figure 1 shows a basic block diagram of a smart lock with an LDO, such as the <a href="http://www.ti.com/product/tps76625" target="_blank">TPS76625</a>. Some engineers consider LDOs because of their cost. In most cases, the integrated circuit (IC) cost of an LDO is lower than the IC cost for a buck (step-down) or boost (step-up) converter. But the efficiency of a linear circuit shortens battery life.</p>
<p align="center"><a href="/cfs-file/__key/communityserver-blogs-components-weblogfiles/00-00-00-09-40/6114.figure1.PNG"><img src="/resized-image/__size/1230x0/__key/communityserver-blogs-components-weblogfiles/00-00-00-09-40/6114.figure1.PNG" alt=" " /></a></p>
<p align="center"><b>Figure 1: Smart-lock block diagram with an LDO</b></p>
<p>Figure 2 shows a block diagram with a boost converter, such as the <a href="http://www.ti.com/product/tps61030" target="_blank">TPS61030</a>. The four AA batteries are rearranged to support the boost topology for the motor driver, while the wireless MCU connects directly to the batteries. While this is very efficient, the high power converted by the boost converter for the motor driver equates to a higher level of power loss in absolute terms. There is a more efficient way.</p>
<p align="center"><b> <a href="/cfs-file/__key/communityserver-blogs-components-weblogfiles/00-00-00-09-40/3443.figure2.jpg"><img src="/resized-image/__size/500x0/__key/communityserver-blogs-components-weblogfiles/00-00-00-09-40/3443.figure2.jpg" alt=" " /></a></b></p>
<p align="center"><b>Figure 2: Smart-lock block diagram with a boost converter</b></p>
<p>Figure 3 shows a block diagram with a buck converter. The efficiency values are specifically taken from the <a href="http://www.ti.com/product/tps62745" target="_blank">TPS62745</a> ultra-low-power buck converter. An ultra-low-power converter greatly increases efficiency in the system’s standby mode. For a smart lock, the system operates in standby, without the lock opening or closing, for almost its entire life.</p>
<p align="center"><a href="/cfs-file/__key/communityserver-blogs-components-weblogfiles/00-00-00-09-40/figure3.jpg"><img src="/resized-image/__size/500x0/__key/communityserver-blogs-components-weblogfiles/00-00-00-09-40/figure3.jpg" alt=" " /></a></p>
<p align="center"><b>Figure 3: Smart-lock block diagram with a buck converter</b></p>
<p>Figure 4 compares the battery life for each topology. This graph assumes that the lock opens or closes 12 times per day. As you can see, battery life is directly proportional to the frequency of connection events from the wireless MCU. The more often it tries to connect – in order to discover someone trying to open the lock – the more power it uses. With a standard connection time of 500ms, 60 months (five years) of battery life is possible with four AA alkaline batteries.</p>
<p align="center"><a href="/cfs-file/__key/communityserver-blogs-components-weblogfiles/00-00-00-09-40/3051.figure4.PNG"><img src="/resized-image/__size/1230x0/__key/communityserver-blogs-components-weblogfiles/00-00-00-09-40/3051.figure4.PNG" alt=" " /></a></p>
<p align="center"><b>Figure 4: Battery lifetime comparison for different power topologies</b></p>
<p>This post offers merely a thumbnail sketch of the different power topologies. I encourage you to read the white paper, “<a href="http://www.ti.com/lit/wp/slyy107/slyy107.pdf" target="_blank">Extending battery life in smart locks</a>,” and look at the <a href="http://www.ti.com/tool/tida-00757" target="_blank">Smart Lock Reference Design Enabling 5+ Years Battery Life on 4x AA Batteries</a>, which both go into more detail.</p><div style="clear:both;"></div><img src="https://e2e.ti.com/aggbug?PostID=669381&AppID=940&AppType=Weblog&ContentType=0" width="1" height="1">Chris Glaserhttps://e2e.ti.com:443/members/1090425How 1.2% more efficiency can help you charge faster and coolerhttps://e2e.ti.com/blogs_/archives/b/fullycharged/posts/how-1-2-more-efficiency-can-help-you-charge-faster-and-cooler2017-01-17T23:12:00Z2017-01-17T23:12:00Z<div><b>Other Parts Discussed in Post: </b><a href="https://www.ti.com/product/BQ25890" class="internal-link folder product" title="Link to Product Folder" target="_blank">BQ25890</a>, <a href="https://www.ti.com/product/BQ25898" class="internal-link folder product" title="Link to Product Folder" target="_blank">BQ25898</a></div><p>With portable products packed with new features and an embedded lithium-ion battery inside, one key design consideration is how to optimize the end-user experience with fast and cool charging. Most higher-current (>1A) portable electronics have adopted a high-efficiency synchronous-switching battery charger with integrated MOSFETs. These chargers provide an efficient charging solution with less heat and longer battery life.</p>
<p>As smartphones, tablets and other portable gadgets feature bigger and higher-capacity batteries, switching charger efficiency is the key to charging them quickly. While consumers may not notice a 1% or 2% charging efficiency difference, they will certainly sense an additional 5 or 10 degrees of heat on the outer surface of their handheld device. Therefore, any portable products where space between the printed circuit board (PCB) and exterior case is tight must have a certain power budget for the heat that fast charging generates.</p>
<p>Figure 1 is an example of a power-loss budget limited at 1.1W. The charger IC is 43<b>°</b>C and the case temperature is 34<b>°</b>C, which is linearly proportional to the power loss in an enclosed case. Thus, consumers will not be able to feel the heat generated inside.</p>
<p><img src="/resized-image/__size/1230x0/__key/communityserver-blogs-components-weblogfiles/00-00-00-03-59/6201.fig1.PNG" alt=" " style="display:block;margin-left:auto;margin-right:auto;" /> </p>
<p align="center"><b>Figure 1: (a) </b>IC 43<b>°</b>C with 1.1W loss (b) case 34<b>°</b>C with 1.1W loss <b></b></p>
<p>Let’s compare two of TI’s switching chargers: the <a href="http://www.ti.com/product/bq25898" target="_blank">bq25898</a> vs. the <a href="http://www.ti.com/product/bq25890" target="_blank">bq25890</a>, with 9V input and 3A charging. The <a href="http://www.ti.com/product/bq25898" target="_blank">bq25898</a> can achieve 1.2% higher charging efficiency compared to the <a href="http://www.ti.com/product/bq25890" target="_blank">bq25890</a>, as shown in Figure 2.</p>
<p align="center"><img src="/resized-image/__size/1230x0/__key/communityserver-blogs-components-weblogfiles/00-00-00-03-59/68334.fig2.PNG" alt=" " /></p>
<p align="center"><b>Figure 2: bq25898 vs. bq25890 Charge Efficiency</b></p>
<p>What does a 1.2% charger-efficiency improvement mean to you? With the same 1.1W loss budget, the bq25898 can deliver 380mA more (13% higher) charging current. And yes, you can charge >3A using the bq25898 charger maintaining the same temperature as the bq25890. The charging current for the bq25890 is about 2.99A with an efficiency of 91.2%; the charging current for the bq25898 is about 3.37A with an efficiency of 92.1%.</p>
<p>Many studies have shown that lithium-Ion batteries suffer capacity degradation over time when exposed to high temperatures. High efficiency is not only good for fast charging but also good for the long-term life of the battery, as well as a consumer’s impression of product quality. Using a high-efficiency battery charger is one of the best ways to minimize heat generation in a portable system and charge up the battery fast.</p>
<p><b>Additional resources</b></p>
<ul>
<li>Read my colleague Upal Sengupta’s blog post, “<a href="http://e2e.ti.com/blogs_/b/powerhouse/archive/2013/04/27/fully-charged-the-path-of-least-resistance" target="_blank">Fully Charged: The Path of Least Resistance</a>.”</li>
</ul><div style="clear:both;"></div><img src="https://e2e.ti.com/aggbug?PostID=669364&AppID=940&AppType=Weblog&ContentType=0" width="1" height="1">Fernando Lopezhttps://e2e.ti.com:443/members/4114769How do you detect battery aging in rarely discharged applications?https://e2e.ti.com/blogs_/archives/b/fullycharged/posts/how-do-you-detect-battery-age-in-rarely-discharged-applications2017-01-10T19:56:00Z2017-01-10T19:56:00Z<div><b>Other Parts Discussed in Post: </b><a href="https://www.ti.com/product/BQ34110" class="internal-link folder product" title="Link to Product Folder" target="_blank">BQ34110</a></div><p style="text-align:left;">Battery packs are used in the products that we depend on daily. Many of our portable devices such as our cell phones, our watches and our tablet computers are constantly at our sides and running on batteries. Consequently, their batteries discharge throughout the day and we have to recharge them every one to two days. We assume that the gauges in these products are accurate and will not leave us stranded between charges. Fortunately, gauges do monitor our batteries accurately and maintain this accuracy by updating the available capacity of the cells as they age. These updates do require that the cell discharge periodically and the depth of the discharge depends on the type of gauge.</p>
<p>Impedance track gauges require at least a 37% discharge and CEDV gauges require almost a full discharge. While this is not a problem on products that we take with us, there are products where discharges are not common and maybe not even allowed. These are referred to as rarely discharged applications and some examples are backup systems, emergency battery power modules and portable computers that you leave plugged in at your desks. Backup systems must maintain a high state-of-charge to be available should a power failure occur. You cannot risk a full discharge or even a 37% discharge and still have enough capacity available for a system backup in most cases.</p>
<p style="text-align:center;"><a href="/cfs-file/__key/communityserver-blogs-components-weblogfiles/00-00-00-09-40/6558.fig1.PNG"><img src="/resized-image/__size/1230x0/__key/communityserver-blogs-components-weblogfiles/00-00-00-09-40/6558.fig1.PNG" alt=" " /></a></p>
<p align="center"><b>Figure 1: CEDV learning profile vs. supporting a backup (a); EOS learning profile vs. supporting a backup (b)</b></p>
<p>The challenge is how to detect that the battery is aging without compromising the capability to support a backup event. TI has developed the new end-of-service (EOS) algorithm to provide an early warning that the pack has lost its ability to support a backup. This algorithm only requires a shallow 1% to 2% discharge to measure the series resistance of the cells. This discharge can occur from the present voltage state or you can charge the pack and then initiate the discharge back down to the current state.</p>
<p>The gauge uses a special filtering algorithm to analyze the series resistance during this “learning phase” and it monitors that resistance over time to detect when it starts increasing significantly. The increase in the series resistance is an indicator that the cells have degraded and may not longer be able to support the backup. The gauge will provide an EOS flag to the host when it determines that the cells need to be replaced.</p>
<p style="text-align:center;"> <a href="/cfs-file/__key/communityserver-blogs-components-weblogfiles/00-00-00-09-40/8625.figure2.png"><img src="/resized-image/__size/500x0/__key/communityserver-blogs-components-weblogfiles/00-00-00-09-40/8625.figure2.png" alt=" " /></a></p>
<p align="center"><b>Figure 2: Series resistance aging detected by the EOS algorithm</b></p>
<p>The bq34110 incorporates the EOS and the CEDV algorithms to provide a full suite of gauging options for the pack. The CEDV algorithm updates the gauging accuracy of the discharge as the cells age. The EOS algorithm (Figure 2) warns the host that the cells need to be replaced, if discharges are not possible to keep the available capacity updated. The device also provides a “learning load” control output to allow the gauge to control the load required to support EOS learning. The gauge will also update the Full Charge Capacity for the CEDV algorithm when a full discharge occurs to provide accurate State-of-Charge estimates for normal discharges. The gauge supports Li-Ion, LiFePO4, Lead Acid and Nickel Metal Hydride (NiMH) cell chemistries and cell stacks up to 65V. If your design does not allow periodic discharge events, then the EOS option may be a good option to know when the cells need to be replaced. The algorithm supports most of the rechargeable battery chemistries and it also supports Lithium primary cells. More information and samples are available on the <a href="http://www.ti.com/product/bq34110" target="_blank">bq34110</a> and <a href="http://www.ti.com/product/bq35100" target="_blank">bq35100</a> product pages. </p>
<p><b>Additional resources: </b></p>
<ul>
<li>Learn more about designing with battery fuel gauges with these blog posts:
<ul>
<li><a href="/blogs_/b/fullycharged/archive/2016/09/26/how-accurate-is-your-gauge-part-1" target="_blank">How accurate is your battery fuel gauge? Part 1/2</a></li>
<li><a href="/blogs_/b/fullycharged/archive/2016/11/04/how-accurate-is-your-battery-fuel-gauge-part-2-2" target="_blank">How accurate is your battery fuel gauge? Part 2/2</a></li>
<li><a href="/blogs_/b/fullycharged/archive/2016/05/26/where-should-i-place-my-battery_1920_s-gas-gauge" target="_blank">Where should I place my battery’s gas gauge?</a></li>
</ul>
</li>
<li>Watch the training video: <a href="https://training.ti.com/why-prefer-using-gauge-primary-cell-and-rarely-discharged-applications-over-maintenance-cycle">Unique Gauging Algorithms for Industrial Applications - Primary Cells & Rarely Discharged Applications</a></li>
<li>For more information on gauging please visit <a href="http://www.ti.com/gauge" target="_blank">www.ti.com/gauge</a>.</li>
</ul>
<p> </p><div style="clear:both;"></div><img src="https://e2e.ti.com/aggbug?PostID=669345&AppID=940&AppType=Weblog&ContentType=0" width="1" height="1">ThomasCosbyhttps://e2e.ti.com:443/members/32754Don’t let your battery drain on the shelf – use ship modehttps://e2e.ti.com/blogs_/archives/b/fullycharged/posts/don-t-let-your-battery-drain-on-the-shelf-use-ship-mode2016-12-27T09:18:00Z2016-12-27T09:18:00Z<p><b> </b><b>Don’t let your battery drain on the shelf – use ship mode</b></p>
<p>You’ve done it; your <a href="http://www.ti.com/solution/power_battery_management" target="_blank">battery-powered design</a> is complete: a new wearable for the consumer electronics market. You’re excited, and you want your consumers to feel that same excitement when they open the box and turn the device on. But how do you make sure that happens? A Christmas present bought in advance can be sitting in wrapping paper for four weeks or more. The last thing you want is for the recipient to find that the battery is dead and spend their first moments with the product waiting for it to charge. But you can ensure a better customer experience by implementing ship mode.</p>
<p>The ship-mode circuit is a circuit which utilizes several components to prolong battery life during electronics shipment and provide customers with a consistent out-of-the-box experience. Ship mode electronically disconnects the battery from the rest of the system to minimize power drain while the product is idle. When the consumer turns the product on for the first time, the battery connects to the rest of the system and stays connected until the system decides to put itself back into ship mode.</p>
<p>Figure 1a shows the behavior of the circuit when in ship mode; Figure 1b shows the circuit out of ship mode.</p>
<p align="center"><a href="/cfs-file/__key/communityserver-blogs-components-weblogfiles/00-00-00-09-40/Ship-mode_5F00_Figure-1.PNG" target="_blank"><img src="/resized-image/__size/1230x0/__key/communityserver-blogs-components-weblogfiles/00-00-00-09-40/Ship-mode_5F00_Figure-1.PNG" alt=" " /></a></p>
<p align="center"><strong>Figure 1: Ship-mode circuit behavior: ship mode (a); out-of-ship mode (b)</strong></p>
<p style="text-align:left;">So what does a ship-mode circuit look like? It needs to be noninvasive to the rest of the design, so the smaller the better. The leakage from the battery to the rest of the system needs to be minimized to prolong battery life. With these things in mind, consider the solution in Figure 2.</p>
<p style="text-align:center;"><strong style="text-align:center;"><a href="/cfs-file/__key/communityserver-blogs-components-weblogfiles/00-00-00-09-40/5736.Figure-2.png" target="_blank"><img src="/resized-image/__size/1230x0/__key/communityserver-blogs-components-weblogfiles/00-00-00-09-40/5736.Figure-2.png" width="405" height="286" alt=" " /></a></strong></p>
<p style="text-align:center;"><strong>Figure 2: Ship-mode circuit using the TPS22916B load switch</strong></p>
<p>The TPS22916B load switch goes between the battery and the system. When the circuit is put into ship mode, the load switch disables and disconnects the battery from the system. Pressing a button on the product causes it to exit ship mode and turn the system on. The load switch is enabled, connecting the battery to the system. Keeping the button depressed keeps the load switch on and the battery stays connected. Pressing a button after the system has exited ship mode provides a signal that the rest of the system can read. This is an advantage for applications with only one button, since that button can both exit ship mode and control the system afterwards.</p>
<p>When in ship mode, the battery is disconnected from the rest of the system. There is a small amount of leakage current caused by the ship-mode circuit, which depends on the load switch you use. When disabled, the TPS22916B has only 10nA of leakage current flowing into the V<sub>IN</sub> pin. This is the only drain on the battery when the system is in ship mode. With the ship-mode circuit, a fully charged 100mAh battery will still be at about a 99.8% battery charge after two years.</p>
<p>To validate this solution, the <a href="http://www.ti.com/tool/TIDA-00556" target="_blank">Load Switch Based Ship Mode Reference Design for Wearables</a> implements the ship-mode circuit in a 1.89mm<sup>2</sup> area and verifies the low leakage current of 10nA. See Figure 3.</p>
<p align="center"><strong><a href="/cfs-file/__key/communityserver-blogs-components-weblogfiles/00-00-00-09-40/Ship-mode_5F00_Figure-3.jpg" target="_blank"><img src="/resized-image/__size/500x0/__key/communityserver-blogs-components-weblogfiles/00-00-00-09-40/Ship-mode_5F00_Figure-3.jpg" alt=" " width="354" height="352" /></a><br /></strong></p>
<p align="center"><strong>Figure 3: Load switch-based ship-mode reference design for wearables</strong></p>
<p>After a year of this reference design board sitting on my desk, the CR2032 battery is still able to power the board. Isn’t it time to let your design do the same? Download this <a href="http://www.ti.com/tool/TIDA-00556" target="_blank">ship mode reference design</a> today to implement ship mode and prevent your battery from draining.</p>
<p><strong>Additional resources</strong></p>
<ul>
<li>Download the following application notes:
<ul>
<li>"<a href="https://www.ti.com/lit/slvaec5" target="_blank">When to Make the Switch to an Integrated Load Switch</a>."</li>
<li>“<a href="http://www.ti.com/lit/slva670a" target="_blank">Managing Inrush Current</a>.”</li>
<li>“<a href="http://www.ti.com/lit/slva652" target="_blank">Load Switches: What Are They, Why Do You Need Them and How Do You Choose the Right One</a>?”</li>
</ul>
</li>
<li>Watch the video, “<a href="https://training.ti.com/how-and-why-replace-discrete-mosfets-load-switches" target="_blank">How and why to replace discrete MOSFETs with load switches</a>.”</li>
<li>Read the following load switch technical articles:
<ul>
<li>“<a href="/blogs_/b/analogwire/archive/2015/02/23/how-to-save-power-using-load-switches" target="_blank">How to save power using load switches</a>.”</li>
<li>“<a href="/blogs_/b/powerhouse/archive/2015/12/05/load-switches-timing-is-everything" target="_blank">Timing is everything with load switches!</a>.”</li>
</ul>
<p style="padding:0;margin:0;"></p>
</li>
</ul><div style="clear:both;"></div><img src="https://e2e.ti.com/aggbug?PostID=669325&AppID=940&AppType=Weblog&ContentType=0" width="1" height="1">Aleksandras_Kakneviciushttps://e2e.ti.com:443/members/3753190How to choose a multicell gaugehttps://e2e.ti.com/blogs_/archives/b/fullycharged/posts/how-to-choose-a-multicell-gauge2016-12-16T22:00:00Z2016-12-16T22:00:00Z<div><b>Other Parts Discussed in Post: </b><a href="https://www.ti.com/product/BQ40Z50-R1" class="internal-link folder product" title="Link to Product Folder" target="_blank">BQ40Z50-R1</a>, <a href="https://www.ti.com/product/BQ28Z610" class="internal-link folder product" title="Link to Product Folder" target="_blank">BQ28Z610</a></div><p><img src="/resized-image/__size/700x0/__key/communityserver-blogs-components-weblogfiles/00-00-00-09-40/battery-gauge2.jpg" style="display:block;margin-left:auto;margin-right:auto;" alt=" " /></p>
<p>A battery gauge is essential in most modern systems to help determine how much power a given system can draw from the battery pack. Whether batteries are the system’s primary or backup power source, in most systems reliably operate on. In most cases, it is not very straightforward to estimate the amount of capacity in battery packs. Depending on the system, there are various factors that need to be understood when selecting the appropriate battery gauge.</p>
<p>A multicell battery refers to more than one series cell in the battery pack. You’ll find multicell battery packs in notebook computers, drones, portable medical equipment, server backup systems and industrial applications.</p>
<p>Some of the most common factors to consider when choosing a multicell battery gauge are cell type and chemistry, number of series/parallel cells and charge/discharge currents, system or pack side.</p>
<p>Let’s take a look at each factor in detail.</p>
<p><b>Cell type and chemistry </b></p>
<p>Cell type and chemistry refers to whether it is a primary cell (not designed to be recharged) or a secondary cell (rechargeable cell), and the type of chemistry used in the cells, such a lithium-ion or lithium-ion phosphate (LiFePO4). Typically, the gauging method for primary cells can be quite different from the method used for rechargeable cells. For primary cells, the gauge does not have to keep track of the number of cycles (charges and discharges) since these cells are not rechargeable. Different algorithms have been optimized to work with either primary or secondary cells. Compensated end of discharge voltage (CEDV) gauges typically work better for primary cells (like in the <a href="http://www.ti.com/product/bq35100" target="_blank">bq35100</a>), while Impedance Track™ gauges work better for secondary cells (like in the <a href="http://www.ti.com/product/bq40z50-r1" target="_blank">bq40z50-R1</a>).</p>
<p>Cell chemistry plays a significant part in the algorithm used for gauging; for example, a lead-acid battery will have to be gauged quite differently than a LiFePO4 battery. Gauges that work independently of battery series cells like the <a href="http://www.ti.com/product/BQ34Z100-G1" target="_blank">bq34z100</a> or <a href="http://www.ti.com/product/bq34110" target="_blank">bq34110</a> are better for lead-acid cells, while the bq40z50-R1 or bq28z610 are better for LiFePO4 cells.</p>
<p><b>Number of series and parallel cells and system load</b></p>
<p>The number of series cells plays an important part in battery-gauge selection. For certain cells, each individual series cell voltage may need monitoring.</p>
<p>The gauge should also be able to handle the capacity of the battery pack, which is determined by the number of parallel cells. For large-series cell counts, gauges like the <a href="http://www.ti.com/product/BQ34Z100-G1" target="_blank">bq34z100</a>, or the <a href="http://www.ti.com/product/bq78350-r1" target="_blank">bq78350-R1</a> will be appropriate, as an external resistor network can divide the voltage down for input into these gauges. For two- to four-series connected Lithium-based cells, the <a href="http://www.ti.com/product/bq40z50-r1" target="_blank">bq40z50-R1</a> is preferred, because it can monitor individual cell voltages and will result in more accurate gauging performance.</p>
<p>Depending on the system load, the gauge should be able to measure the discharge and charge current dictated by the system.</p>
<p><b>System- or pack-side gauge</b></p>
<p>System-side gauges are integrated into the system; the cells are usually replaceable. Pack-side gauges are gauges integrated into the battery pack that track the health and state of charge of the cells they accompany.</p>
<p>Pack-side gauges will incorporate a gauge for each of the battery pack for rechargeable cells, but provide much better accuracy over the life of the pack. For primary cells or where the battery pack is very cost-sensitive, a system-side gauge will be the better option. CEDV (<a href="http://www.ti.com/product/bq4050" target="_blank">bq4050</a>) gauges are the better choice for system-side gauges since the gauge will not be required to keep track of the impedance and charge/discharge cycles run on the cells and Impedance Track™ technology-based gauges (bq40z50-R1) are a better choice for pack-side gauges as it can keep track of the impedance and cycle count on the cells and provide more accurate state of charge.</p>
<p><a href="http://www.ti.com/lsds/ti/power-management/battery-fuel-gauge-overview.page" target="_blank">TI’s battery fuel gauge product page</a> helps use the criteria I’ve described in this post to recommend the best battery gauge that will work for an application. What applications would you like to see gauges designed into in the future?</p>
<p> </p>
<p><strong>Additional resources:</strong></p>
<ul>
<li>Learn more about working with gauges in this blog series: <a href="http://e2e.ti.com/blogs_/b/fullycharged/archive/2016/09/26/how-accurate-is-your-gauge-part-1" target="_blank">How accurate is your battery fuel gauge?</a></li>
</ul><div style="clear:both;"></div><img src="https://e2e.ti.com/aggbug?PostID=669313&AppID=940&AppType=Weblog&ContentType=0" width="1" height="1">Swaminathan Ramanathan75031https://e2e.ti.com:443/members/1995515Make your power bank more reliable with output short-circuit protectionhttps://e2e.ti.com/blogs_/archives/b/fullycharged/posts/make-your-power-bank-safer-with-output-short-circuit-protection2016-12-06T14:00:00Z2016-12-06T14:00:00Z<p><span style="font-family:inherit;font-size:inherit;">Lithium ion (Li-Ion) or lithium polymer (LiPo) batteries are key components in some portable systems, especially power banks. But on rare occasions, these batteries have the potential risk of catching on fire or even exploding in short-circuit, overvoltage or high-temperature conditions. An increasing number of such incidences are occurring even today.</span></p>
<p><span style="font-family:inherit;font-size:inherit;">To hel</span>p safeguard consumers against these conditions, Underwriters Laboratories (UL) announced the first dedicated safety standard for the power bank industry at the end of 2015. One of the key test items is the output power overload test, which presents a new challenge for power bank designers. Because most power banks don’t have output short-circuit protection functions, they can easily fail the overload test.</p>
<p>In fast-charge power banks with high battery capacities, there’s a high-power boost converter between the power bank’s internal battery and its output port. We know some designers want to achieve output short-circuit protection by using an MCU (which already exists in power bank systems) to judge the boost converter’s output current. The designers put a sense resistor and a power MOSFET in the <a href="http://www.ti.com/lsds/ti/power-management/boost-converter-integrated-switch-products.page" target="_blank">boost converter</a>’s output return and sense the output current by detecting the voltage, V<sub>SENSE</sub>, across the sense resistor. The MCU’s analog to digital converter (ADC) pin samples the V<sub>SENSE</sub> and compares it with the internal overcurrent protection point. If V<sub>SENSE</sub> is higher than the target value, one of the MCU’s input/output (I/O) pins will go high and the power MOSFET in the return path will turn off, disconnecting the <a href="http://www.ti.com/lsds/ti/power-management/boost-converter-integrated-switch-products.page" target="_blank">boost converter</a> from the load.</p>
<p>The logic of this protection solution is fine, but it does not work in practice. Why? The problem comes from the MCU’s long response time. The MCU will need at least several milliseconds before taking action in a short-circuit condition. In the meantime, the <a href="http://www.ti.com/lsds/ti/power-management/boost-converter-integrated-switch-products.page" target="_blank">boost converter</a>’s input and output current will reach a very high value before they can be disconnected from the load. This high short-circuit current can damage the battery and cause other issues.</p>
<p>What if the battery itself has overcurrent protection? It can disconnect from the boost converter within several hundred microseconds in a short-circuit condition. Could you remove the short-circuit protection circuit in this case? The answer is no. Once the battery protects itself by disconnecting from the boost converter, it needs to reactivate to connect with the boost converter again. The power bank can’t charge the end equipment during this period, making consumers apt to believe there is a problem with their device when in fact the device is performing self-protection features. . This gives power bank designers a need to disconnect the <a href="http://www.ti.com/lsds/ti/power-management/boost-converter-integrated-switch-products.page" target="_blank">boost converter</a> from the load as quickly as possible in a short circuit condition to avoid the battery’s self-protection and a gap in power bank functionality.</p>
<p>The <a href="http://www.ti.com/lit/ug/tidubu0/tidubu0.pdf" target="_blank">TI Designs Output Short-Circuit Protection Reference Design for the TPS61088 Boost Converter (PMP9779)</a> is designed to solve this problem. The key advantage of the design is its fast protection speed: The total response time is only about 5µs. Let’s take a look at the implementation (Figure 1).</p>
<p align="center"><a href="/cfs-file/__key/communityserver-blogs-components-weblogfiles/00-00-00-09-40/5127.fig1.PNG"><img alt=" " src="/resized-image/__size/800x0/__key/communityserver-blogs-components-weblogfiles/00-00-00-09-40/5127.fig1.PNG" /></a></p>
<p align="center"><b>Figure </b><b>1</b><b>: Block diagram of the <a href="http://www.ti.com/tool/pmp9779" target="_blank">Output Short-Circuit Protection Reference Design for the TPS61088 Boost Converter</a> </b></p>
<p align="center" style="text-align:left;">A shunt resistor, RS, placed in the boost converter’s output return path converts the output current to a voltage signal, V<sub>SENSE</sub>. In an overload or output short-circuit condition, V<sub>SENSE</sub> will be higher than the reference voltage, V<sub>REF</sub>. Thus, the <a href="http://www.ti.com/product/tl331">TL331</a> comparator’s output signal, V<sub>O_TL331</sub>, goes high. Q2 turns on and pulls down the Q1’s gate-drive voltage to ground. So Q1turns off. The <a href="http://www.ti.com/product/tps61088">TPS61088</a> boost converter is completely disconnected from the load. The hysteresis comparator circuit helps Q1 avoid from turning on and off frequently before fault clearing. Once the output overload or short-circuit condition is cleared, the circuits can recover by toggling (disabling then enabling) the <a href="http://www.ti.com/product/tps61088">TPS61088’s</a> EN pin.</p>
<p>Figure 2 shows the output short-circuit protection performance at a V<sub>OUT</sub> = 5V condition. From the waveforms of the Q1’s gate-drive signal, Vgs_Q1, and the output current I<sub>O</sub>, you can see that the <a href="http://www.ti.com/product/tps61088" target="_blank">TPS61088</a> can disconnect from the load within 5µs in an output short-circuit condition. The input current of the boost converter, which is also the output current of the battery, is well limited and doesn’t rise to a very high value because of the fast protection speed, preventing the battery’s self-protection function from triggering.</p>
<p align="center"><a href="/cfs-file/__key/communityserver-blogs-components-weblogfiles/00-00-00-09-40/2465.fig2.PNG"><img alt=" " src="/resized-image/__size/800x0/__key/communityserver-blogs-components-weblogfiles/00-00-00-09-40/2465.fig2.PNG" /></a></p>
<p align="center"><b>Figure 2: Output short-circuit performance at V<sub>OUT</sub> = 5V (V<sub>IN</sub> = 3.6V)</b></p>
<p>With the above simple yet effective OCP protection circuit, the <a href="http://www.ti.com/product/tps61088" target="_blank">TPS61088</a> boost converter can be disconnected from the load within 5us, which makes your power bank more reliable in the output short circuit condition. Besides power bank applications, this TI design also fit for blue-tooth speaker, portable POS terminals applications and more.</p>
<p>In what other applications could you use this protection method?</p>
<p><b>Additional resources: </b></p>
<ul>
<li>Read my last blog: <a href="http://e2e.ti.com/blogs_/b/fullycharged/archive/2016/08/24/pass-your-power-bank-emi-test" target="_blank">Pass your power bank EMI test</a></li>
<li>Learn more about power banks with these <a href="http://e2e.ti.com/tags/power%2bbanks" target="_blank">blog posts.</a></li>
</ul><div style="clear:both;"></div><img src="https://e2e.ti.com/aggbug?PostID=669002&AppID=940&AppType=Weblog&ContentType=0" width="1" height="1">Helen chenhttps://e2e.ti.com:443/members/4197150A step-by-step guide to calculating battery gauge accuracyhttps://e2e.ti.com/blogs_/archives/b/fullycharged/posts/how-accurate-is-your-battery-fuel-gauge-part-2-22016-11-04T22:33:00Z2016-11-04T22:33:00Z<div><b>Other Parts Discussed in Post: </b><a href="https://www.ti.com/tool/BQSTUDIO" class="internal-link folder tool" title="Link to Tool Folder" target="_blank">BQSTUDIO</a></div><p><b>Step-by-step calculation of gauging accuracy and other factors affecting accuracy</b></p>
<p>In part 1 of this series, I discussed the difference between measurement accuracy and gauging accuracy. I highlighted that gauging accuracy depends on the accuracy of input variables (voltage, current and temperature) into your chosen algorithm, as well as the algorithm’s robustness, or the ability to account for different battery use cases. I also pointed out that you can quickly evaluate the accuracy of a gauge by inspecting the state of charge to confirm that the gauge reports 0% near the terminate voltage and that the SOC doesn’t experience significant jumps.</p>
<p>An even more effective method is to compute gauge accuracy across the battery’s entire discharge profile. You can do this with the charge profile as well, but because users are more concerned about accuracy during battery discharge, accuracy is often evaluated using the battery discharge profile.</p>
<p>Here is a step-by-step method to calculate gauging accuracy: (Download this <a href="https://www.ti.com/graphics/reserved/eugraphics/AccuracyWalk_Through.xlsx">Excel sheet</a> has actual numbers and formulas)</p>
<p>1. <strong>Start with a gauge log</strong> in <a href="https://www.ti.com/graphics/reserved/eugraphics/AccuracyWalk_Through.xlsx" rel="noopener noreferrer" target="_blank">Excel</a> of the voltage, current, temperature and reported SOC. In part 1 of this series, I mentioned that you can extract the gauge log using bqStudio and a TI gauge EVM or any gauge and an Arbin or Maccor. In this example, I will describe the process using a gauge log from bqStudio and a TI gauge EVM.</p>
<p>2. <strong>Create a new column for calculated passed charge (dQ)</strong>. The log file should start from a fully charged state and end at the terminate voltage, where empty is reached (or wherever discharge stops). Use the Excel formula below to calculate each row of passed charge:</p>
<ul>
<li>Calculated_dQ = rolling sum of current_reading * time_since_last_log_point.</li>
<li>Excel formula: (ElapsedTime<sub>N+1</sub> – ElapsedTime<sub>N</sub>)*|AvgCurrent<sub>N</sub>| /3600+ Calculated_dQ<sub>N-1</sub>. (Since the unit of elapsed time is in seconds, convert it to hours by dividing by 3,600. Calculated_dQ<sub>N-1</sub> is the immediate previously calculated passed charge.)</li>
</ul>
<p>3. <strong>Calculate the battery’s true full-charge capacity</strong>, which is the sum of all the passed charge:</p>
<ul>
<li>FCC_true = integrated capacity, from fully charged state down to termination voltage.</li>
</ul>
<p>4. <strong>Create a new column and calculate the battery’s remaining capacity</strong> <strong>(Calculated_RM)</strong> at each point along the discharge profile:</p>
<ul>
<li>Calculated_RM = FCC_true – Calculated_dQ.</li>
<li>Excel formula: $FCC_true – Calculated_dQ<sub>N</sub>.</li>
</ul>
<p>5. <strong>Calculate the battery’s true state of charge</strong> <strong>(Calculated_SOC)</strong> in percentage at each point in a new column:</p>
<ul>
<li>Calculated_SOC = Calculated_RM / FCC_true * 100.</li>
<li>Excel formula: Calculated_RM / $FCC_true * 100.</li>
</ul>
<p>6. <strong>Calculate the state-of-charge error</strong> reported by the gauge at each point in a new column by subtracting the state of charge reported by the gauge from the calculated state of charge:</p>
<ul>
<li>SOC_error = SOC_true – SOC_gauge.</li>
<li>Excel formula: Calculated_SOC<sub>N</sub> – SOC_gauge<sub>N</sub>.</li>
</ul>
<p>The <a href="http://www.ti.com/webemail/graphics/dm4727/AccuracyWalk_Through.zip" rel="noopener noreferrer" target="_blank">Excel sheet</a> shows the calculation details. In Figure 1, the different highlighted columns represent the different steps in the calculations. As you can see in column M, the SOC error magnitude clearly quantifies gauge accuracy.</p>
<p style="text-align:center;"> <a href="/cfs-file/__key/communityserver-blogs-components-weblogfiles/00-00-00-09-40/8244.fig1.png"><img alt=" " src="/resized-image/__size/600x0/__key/communityserver-blogs-components-weblogfiles/00-00-00-09-40/8244.fig1.png" /></a></p>
<p align="center"><b>Figure 1: Excel log showing an example for calculating SOC error</b></p>
<p>Figure 2 compares the calculated SOC and the SOC reported by the gauge across the battery’s entire discharge profile, while Figure 3 shows the magnitude of the SOC error graphically. In this particular example, you can see that the error in gauge accuracy across the entire discharge profile is less than 2%.</p>
<p style="text-align:center;"><b> <a href="/cfs-file/__key/communityserver-blogs-components-weblogfiles/00-00-00-09-40/7658.fig2.PNG"><img alt=" " src="/resized-image/__size/500x0/__key/communityserver-blogs-components-weblogfiles/00-00-00-09-40/7658.fig2.PNG" /></a></b></p>
<p align="center"><b>Figure 2: Visualization of calculated SOC vs. reported SOC across the battery’s voltage discharge profile</b></p>
<p style="text-align:center;"> <b> <a href="/cfs-file/__key/communityserver-blogs-components-weblogfiles/00-00-00-09-40/60057.fig3.PNG"><img alt=" " src="/resized-image/__size/500x0/__key/communityserver-blogs-components-weblogfiles/00-00-00-09-40/60057.fig3.PNG" /></a></b></p>
<p align="center"><b>Figure 3: Visualization of SOC error across the battery’s entire voltage discharge profile</b></p>
<p>Changes in ambient temperature and discharge current rate can cause the battery capacity (FCC) to increase or decrease, which is an inherent battery characteristic. These changes result in sudden jumps in the state of charge, leading to an unpleasant user experience. In order to curb this, most Texas Instruments gas gauges have a special feature called smoothing. The smoothing algorithm’s main goal is to smooth out the jumps in remaining capacity and SOC over the course of battery charge or discharge. Note that if this functionality is enabled, the gauge’s reported remaining capacity and SOC will be mathematically modified and may not be a true representation of the battery’s state of charge. When calculating accuracy if this filtering is enabled, determine whether you want to use the smoothed (filtered) values or the true values: the gauge has the capability to report both.</p>
<p>Figure 4 compares the calculated actual SOC, the gauge-reported filtered SOC and the gauge-reported true SOC under multiload levels. You can see that the gauge-reported filtered SOC closely follows the gauge-reported true SOC.</p>
<p>Figure 5 compares a gauge-reported SOC error and a gauge-reported filtered SOC error. A more visible difference between the filtered and true gauge SOC would occur if there was a steep temperature change, which will result in a battery capacity change.</p>
<p style="text-align:center;"> <a href="/cfs-file/__key/communityserver-blogs-components-weblogfiles/00-00-00-09-40/3438.fig4.png"><img alt=" " src="/resized-image/__size/800x0/__key/communityserver-blogs-components-weblogfiles/00-00-00-09-40/3438.fig4.png" /></a></p>
<p align="center"><b>Figure 4: Comparison between the battery’s calculated true and gauge-reported SOC under multicurrent levels</b></p>
<p style="text-align:center;"><a href="/cfs-file/__key/communityserver-blogs-components-weblogfiles/00-00-00-09-40/1881.fig5.png"><img alt=" " src="/resized-image/__size/600x0/__key/communityserver-blogs-components-weblogfiles/00-00-00-09-40/1881.fig5.png" /></a></p>
<p align="center"><b>Figure 5: Comparison of gauge-reported SOC errors across the battery’s voltage profile under multicurrent levels</b></p>
<p>Most gauge users need some capacity in the battery reserved when the gauge reports 0% without hitting the terminate voltage so that the host processor can perform a controlled system shutdown. In cases like this, when evaluating for accuracy, do not carry out your calculations down to the terminate voltage; rather, calculate to whatever voltage threshold corresponds to the amount of reserve capacity you need left in your battery.</p>
<p>Another factor affecting gas gauge accuracy over a battery’s lifetime is the gauge’s ability to track the battery’s changing impedance, which increases as the battery ages. TI’s Impedance Track™ gauging algorithm offers up to 99% accuracy over a battery’s lifetime due to its ability to track the battery’s changing resistances. Our compensated end of discharge voltage (CEDV) gauging algorithm offers up to 98% accuracy and accounts for aging mathematically, using a battery model that may become less accurate as the cell ages. Our Impedance Track-Lite algorithm is a simplified version offering up to 95% accuracy.</p>
<p>In summary, calculating state-of-charge error is a more robust method for evaluating gas gauge accuracy when compared to visual inspection, given that it provides the magnitude of error across the entire battery profile. Other considerations affecting gauge accuracy and its evaluation are smoothing activation, reserve capacity functionality and the gauge algorithm’s ability to track cell aging. For a comprehensive list of the various gauge offerings, visit ti.com/gauges.</p>
<p><b>Additional resources</b></p>
<ul>
<li>Read part 1 of this blog post: How accurate is your battery fuel gauge? Part 1/2.</li>
</ul>
<div style="clear:both;"></div><img src="https://e2e.ti.com/aggbug?PostID=669212&AppID=940&AppType=Weblog&ContentType=0" width="1" height="1">Onyx Ahiakwohttps://e2e.ti.com:443/members/1864200Wireless power during the zombie apocalypsehttps://e2e.ti.com/blogs_/archives/b/fullycharged/posts/the-coming-zombie-apocalypse-and-wireless-power2016-10-28T22:09:00Z2016-10-28T22:09:00Z<p align="center"><img src="/resized-image/__size/400x0/__key/communityserver-blogs-components-weblogfiles/00-00-00-09-40/creepy_5F00_EVMgray-_2800_2_2900_.jpg" alt=" " /></p>
<p>Did you know, the Centers for Disease Control and Prevention has a web page from the Office of Public Health Preparedness and Response to address <a href="http://www.cdc.gov/phpr/zombies.htm" target="_blank">zombie preparedness</a>. They claim that it is tongue in cheek, but we all know better.</p>
<p>Here’s a horrifying thought, what happens when things go south and the zombies start roaming? How will I keep my personal electronics (phone, tablet, watch and others) charged? What if I’m attacked and get zombie brain matter all over my USB connectors? As part of my zombie apocalypse preparedness measures, I’ve started stocking up on spare rechargeable batteries and buying wireless powered devices whenever I can. </p>
<p>The Wi-Fi®, LTE and <i>Bluetooth®</i> in my valuable electronics will transfer data through the gore, but, their batteries need to be recharged too. But, how do I get a decent charge? That’s where wireless power comes in. As long as my home base is safe, I can keep my power transfer going. After wiping away whatever gets on my phone I can place it on the charging pad and get a full recharge.</p>
<p>I’ve even taken the liberty of modifying some of my important electronics to add wireless power. Monitoring my healthy activities can’t stop just because of a zombie or two. I’ll need to keep my fitness tracker running. Gotta keep that heart rate monitored. And what about playing a game or two on my favorite app? What does wireless power have to do with this? I’ve seen enough of the movies to know things can get very messy. I need the <i>Bluetooth®</i> speaker to either broadcast my personal theme song, or find out what tunes drive the zombies mad. Yes, I’ve thought about this a lot.</p>
<p>While I prefer to buy the devices with wireless power built in, there are after-market products that supply wireless power. I also create my own wireless powered electronics. I start with the receiver portion, where I have several good choices. TI’s <a href="http://www.ti.com/product/bq51222" target="_blank">bq51222</a> is a great multipurpose solution. It’s fully certified to the latest Wireless Power Consortium (WPC) v1.2 and Power Matters Alliance (PMA) standards. With the adjustable output voltage feature, I simply adjust the output to the desired voltage (generally 5V for USB, but you can set it up to 8V). To keep the USB option available after I add wireless power, I add a simple dual FET like the <a href="http://www.ti.com/product/csd75207w15" target="_blank">CSD75207W15</a> NexFET™ power MOSFET between the USB input supply and the <a href="http://www.ti.com/product/bq51222" target="_blank">bq51222</a> output. This prevents any power contention if I’ve got both USB power and wireless power active at the same time.</p>
<p>Other options include the <a href="http://www.ti.com/product/bq51013B" target="_blank">bq51013B</a> (another 5W solution) or the <a href="http://www.ti.com/product/bq51003" target="_blank">bq51003</a> for the smaller wearables requiring less than 2.5W. For higher powered solutions (tablets and some fast-charging phones), I like the <a href="http://www.ti.com/product/bq51025" target="_blank">bq51025</a> since it is fully Qi-certified at 5W and can also deliver 10W when paired with the right transmitter.</p>
<p>Speaking of transmitters, for the 5W, I like the <a href="http://www.ti.com/product/bq500511a" target="_blank">bq500511A</a> and <a href="http://www.ti.com/product/bq50002a" target="_blank">bq50002A</a> two-chip solution due to its small BOM count. The newly released <a href="http://www.ti.com/product/bq501210">bq501210</a> 15W transmitter is WPC v1.2 certified. . It works with all 5W Qi-certified receivers, will get that 10W out of the <a href="http://www.ti.com/product/bq51025" target="_blank">bq51025</a> and can deliver 15W with the right receivers. There are several TI Designs that can help you on the wireless power learning curve. The <a href="http://e2e.ti.com/support/power_management/battery_management/" target="_blank">E2E™ Community Battery Management forum</a> is a great way to get detailed design help from experts on TI’s entire product portfolio.</p>
<p>Last, but not least, if you’d like to hear about how to get your batteries fully charged in the quickest time and how to make sure your battery powered taser has full capacity, let me know in the comments below.</p>
<p>Additional resources:</p>
<ul>
<li>Check out the <a href="http://www.ti.com/product/bq501210" target="_blank">15-W wireless power transmitter</a>. </li>
<li>Read more <a href="/tags/wireless%2bpower">wireless power blogs</a>.</li>
<li>Learn more about <a href="http://www.ti.com/wirelesspower" target="_blank">wireless power. </a> </li>
</ul>
<p> </p><div style="clear:both;"></div><img src="https://e2e.ti.com/aggbug?PostID=668921&AppID=940&AppType=Weblog&ContentType=0" width="1" height="1">Dick Staceyhttps://e2e.ti.com:443/members/7867Protecting your battery isn’t as hard as you thinkhttps://e2e.ti.com/blogs_/archives/b/fullycharged/posts/protecting-your-battery-isn-t-as-hard-as-you-think2016-10-17T15:20:00Z2016-10-17T15:20:00Z<div><b>Other Parts Discussed in Post: </b><a href="https://www.ti.com/product/BQ77905" class="internal-link folder product" title="Link to Product Folder" target="_blank">BQ77905</a></div><p align="center"><a href="/cfs-file/__key/communityserver-blogs-components-weblogfiles/00-00-00-09-40/2845.Capture.PNG"><img src="/resized-image/__size/600x0/__key/communityserver-blogs-components-weblogfiles/00-00-00-09-40/2845.Capture.PNG" alt=" " /></a></p>
<p align="center"><b><a href="http://www.ti.com/tool/bq77905evm-707" target="_blank">bq77905 3S to 5S Advanced Stackable Low Power Battery Protector EVM</a></b></p>
<p>When it comes to any type of protection, the solution should be simple. Protection should be something that you design and set up once and don’t have to worry about again; at least that’s how it should be. But when it comes to more and better battery protection, designers may worry about what this might cost them going forward.</p>
<p>Given that battery protection circuitry usually sits inside the battery pack out of sight and isn’t typically considered a cool, sleek new application feature, the design engineer may not give it much thought. But as we’ve learned from recent events, battery-protection can cause major headlines if not done properly.</p>
<p>In general, for any protection device you want the setup to be simple: an IC that protects your system but does not come with a huge “price tag” in terms of high current consumption. Here is where TI’s <a href="http://www.ti.com/product/bq77905" target="_blank">bq77905</a> family of battery protectors for three- to five-series cells and beyond help by providing the protection your system needs with the lowest power drain.</p>
<p>In battery applications you always need to have a primary protector that will serve as the first line of defense and any protection after will have the role of secondary protection. Secondary protection, to briefly mention, allows for last resort type of battery protection which is usually simple over-voltage protection. To learn more about battery protection you can visit my blog, <a target="_blank">Get to know your battery pack: Part 1</a>.</p>
<p>The bq77905 is a great primary protector for applications such as power tools; garden tools; vacuums; and robotic applications like drones, robotic vacuums and robotic lawnmowers. These types of industrial consumer applications take a toll on their battery packs, since consumers want their power tool or robotic vacuum to immediately perform as if it were AC-powered. Typical current consumptions for these applications can go as high as 50A (power tools) and as low (but still high) as 15A continuous current (vacuums). In addition to supporting high current draws, the internal battery pack circuitry needs to consume ultra-low power for longer battery lifetimes and overall runtime.That is where the bq77905’s 6µA of average current consumption really comes in handy.</p>
<p>Industrial consumer applications typically include battery-pack sizes of 3S (small power tools or drones), 4S (drones), 5S (professional power tools), 6S (industrial drones), 7S (vacuums), 10S (garden tools or larger power tools like saws) and even 20S. To accommodate these various sizes, creating a common platform for battery-pack design eliminates the engineering costs associated with redesign and unfamiliarity between different IC architectures. The bq77905 also offers the capability of stacking to provide cell count flexibility to your design.</p>
<p>In general, protection should be straightforward, easy to use and should not cost much (power consumption, price, safety). In addition, you want your protection devices to provide flexibility for your design to allow scalable approaches for various cell counts, which help in overall design cost. Protection should never limit what the application can do.</p>
<p><strong>Additional resources:</strong></p>
<ul>
<li>Explore <a href="http://www.ti.com/lsds/ti/power-management/battery-monitor-protection-and-authentication-solutions-products.page#p404=Protection" target="_blank">TI’s battery protection devices</a>.</li>
<li>Check out the <a href="http://www.ti.com/tool/bq77905evm-707" target="_blank">bq77905 3S to 5S Advanced Stackable Low Power Battery Protector EVM.</a></li>
</ul>
<p> </p><div style="clear:both;"></div><img src="https://e2e.ti.com/aggbug?PostID=669052&AppID=940&AppType=Weblog&ContentType=0" width="1" height="1">Miguel Angel Rioshttps://e2e.ti.com:443/members/3449690How active and passive cell balancing workshttps://e2e.ti.com/blogs_/archives/b/fullycharged/posts/how-active-and-passive-cell-balancing-works2016-10-05T16:16:00Z2016-10-05T16:16:00Z<p><span style="font-family:inherit;font-size:inherit;">In a Power Systems Design article, “<a href="http://www.powersystemsdesign.com/digital-issues" target="_blank">Active and passive balancing for battery management systems</a> (North America > December 2015 > Page 21),” Stefano Zanella described how a multicell system becomes unbalanced. In this post, I would like to explore how batteries become unusable if they’re not balanced and expand a bit on the effects of battery-capacity mismatch. I will focus on automotive lithium-ion (Li-ion) batteries, but in general these principles apply to all batteries.</span></p>
<p><span style="font-family:inherit;font-size:inherit;">Multicell batteries are often built as an array of cells, in series and or in parallel. A higher number of cells in series will lead to higher battery-pack voltages, while more cells in parallel will lead to higher overall battery capacity (expressed as ampere-hour rating, or Ahrs). The battery capacity </span>will then dictate the number of cells in parallel, by the capacity being equal to the number of cells in parallel times the cell capacity required for the system to run. Automotive vehicles tend to use 96 Li-ion cells in series and 24 cells in parallel, depending on cell type. For instance, an electric vehicle with a range of 100 miles will need a battery from 20-30kWh, depending on the weight of the vehicle, the anticipated usage profile and the efficiency of the various systems in the car. Several aspects of the system will dictate the battery-pack voltage, including the overall size and type of the electric motor, cable size, and isolation requirements.</p>
<p>Multicell batteries charge by supplying current to the positive terminal of the cell on top of the stack. (Assume that the battery comprises n cells in series.) In other words, the cells of the battery do not charge individually. If you read Stefano’s article, you already know that at the end of a charge, the amount of charge left in each cell is different; and as you repeatedly charge and discharge the battery (in the absence of balancing), this difference increases. This animation below shows this process.</p>
<p><a href="/cfs-file/__key/communityserver-blogs-components-weblogfiles/00-00-00-09-40/active-passive-cell-balancing.PNG"><img src="/resized-image/__size/1000x0/__key/communityserver-blogs-components-weblogfiles/00-00-00-09-40/active-passive-cell-balancing.PNG" style="display:block;margin-left:auto;margin-right:auto;" alt=" " /></a></p>
<p align="center"><b>Figure 1: How active and passive cell balancing works</b></p>
<p>If you imagine the two cells in Figure 1 as identical containers of charge, driving an electric vehicle will result in extracting energy from the battery, which will deplete those containers. Charging an electric vehicle injects charge into the battery, thereby filling those containers. Not all cells are identical to one another, nor do they age evenly; therefore, the weaker cells will charge and discharge at a slightly different rate. The voltage level of each cell will slowly rise and fall as the cells charge and discharge, respectively.</p>
<p>Let’s start from a full battery. All of the energy (usable energy) contained in the cells can power a car. To not overdischarge the cells (because overdischarging reduces cell lifetimes and can impact safety), when the first cell reaches the undervoltage threshold (plus a safety margin that often depends on the protector), discharging must stop. To not overcharge Li-ion cells, when the first cell reaches the overvoltage threshold, charging must stop. The cells that lag, however, are not fully charged yet, leaving some energy in the battery that cannot be used for driving because, again, when the first cell is full, charging must stop.</p>
<p>In other words, after the first charge/discharge cycle, some energy is stranded in the pack. It can never be used to power the car.</p>
<p>As the battery charges and discharges over and over, the stranded energy increases, thus decreasing the usable energy. Plus, the loss of usable energy is twice the stranded energy because the stranded energy isn’t usable and an equivalent amount of charge cannot be injected into the other cell.</p>
<p>After enough charge and discharge cycles, the usable energy starts to approach zero. How do you avoid this problem? Balancing! You can achieve cell balancing by dissipating the stranded energy onto a resistor, regaining the ability to top off the cells and reach full charge.</p>
<p>As long as all cells have the same capacity, complete balancing is not necessary at the end of each and every charge cycle – because the effects of charge imbalance are fully reversible. I have seen a case during battery electronics development where the passive-balancing portion of a battery was not implemented until after a number of charge/discharge cycles. When the balancing system was ready, the usable energy had diminished by more than 25%. However, after balancing all of the cells, the pack could be fully charged with only a minimal loss of usable energy.</p>
<p>You should choose the amount of balancing current based on the application and thermal considerations. For example, in a 24kWh system (96 cells in series), assuming that the cells have less than a 1% charge-time difference at their end of life (differences in charge times increase over time), a 66Ah system will need to compensate for 660mAh. With a balancing current of 200mA, you could balance this system in 3.3 hours, but it would take twice as much time to balance with a 100mA current.</p>
<p style="text-align:center;"></p>
<p style="text-align:center;"></p>
<p style="text-align:center;"></p>
<table border="1" cellspacing="0" cellpadding="0" style="margin-left:auto;margin-right:auto;">
<tbody>
<tr>
<td width="160" valign="top">
<p><b>Application</b></p>
</td>
<td width="160" valign="top">
<p><b># cells in a series</b></p>
</td>
<td width="264" valign="top">
<p><b>TI monitoring and protection parts</b></p>
</td>
</tr>
<tr>
<td width="160" valign="top">
<p>Laptop/tablet</p>
</td>
<td width="160" valign="top">
<p>2-4</p>
</td>
<td width="264" valign="top">
<p><a href="http://www.ti.com/product/bq40z50-r1">BQ40z50-R1</a>, <a href="http://www.ti.com/product/bq2947?keyMatch=bq294700&tisearch=Search-EN-Everything">BQ2947</a></p>
</td>
</tr>
<tr>
<td width="160" valign="top">
<p>Power tools and garden tools</p>
</td>
<td width="160" valign="top">
<p>3-16</p>
</td>
<td width="264" valign="top">
<p><a href="http://www.ti.com/product/BQ76930" target="_blank">BQ76930</a>, <a href="http://www.ti.com/product/bq76920">BQ76920</a>, <a href="https://www.ti.com/product/BQ76925">BQ70625</a>, <a href="https://www.ti.com/product/BQ76942">BQ76952</a></p>
</td>
</tr>
<tr>
<td width="160" valign="top">
<p>E-bike</p>
</td>
<td width="160" valign="top">
<p>7-16</p>
</td>
<td width="264" valign="top">
<p><a href="http://www.ti.com/product/BQ76930" target="_blank">BQ76930,</a> <a href="http://www.ti.com/product/bq76940">BQ76940</a>, <a href="http://www.ti.com/product/bq76pl455a-q1">BQ76Pl455A-Q1</a>, <a href="http://www.ti.com/product/bq78350-r1">BQ78350-R1</a>, <a href="https://www.ti.com/product/BQ76942">BQ76952</a></p>
</td>
</tr>
<tr>
<td width="160" valign="top">
<p>EV/HEV/PHEV</p>
</td>
<td width="160" valign="top">
<p>60-96</p>
</td>
<td width="264" valign="top">
<p><a href="http://www.ti.com/product/bq76pl455a-q1">BQ76Pl455A-Q1</a>, <a href="http://www.ti.com/product/BQ76PL536A-Q1">BQ76PL536A-Q1</a></p>
</td>
</tr>
<tr>
<td width="160" valign="top">
<p>Micro-hybrid</p>
</td>
<td width="160" valign="top">
<p>4-6</p>
</td>
<td width="264" valign="top">
<p><a href="http://www.ti.com/product/BQ76PL536A-Q1">BQ76PL536A-Q1</a></p>
</td>
</tr>
<tr>
<td width="160" valign="top">
<p>Mild-hybrid</p>
</td>
<td width="160" valign="top">
<p>12-16</p>
</td>
<td width="264" valign="top">
<p><a href="http://www.ti.com/product/bq76pl455a-q1">BQ76PL455A-Q1</a></p>
</td>
</tr>
<tr>
<td width="160" valign="top">
<p>eCall</p>
</td>
<td width="160" valign="top">
<p>1-2</p>
</td>
<td width="264" valign="top">
<p><a href="http://www.ti.com/product/bq76pl455a-q1">BQ76PL455A-Q1</a>, <a href="http://www.ti.com/product/emb1428q">EMB1428Q</a>, <a href="http://www.ti.com/product/EMB1499Q">EMB1499Q</a>, <a href="https://www.ti.com/product/BQ34210-Q1">BQ34210-Q1</a></p>
</td>
</tr>
<tr>
<td width="160" valign="top">
<p>Telecom, UPS, ESS</p>
</td>
<td width="160" valign="top">
<p>10-16</p>
</td>
<td width="264" valign="top">
<p><a href="http://www.ti.com/product/bq76940">BQ76940</a>, <a href="http://www.ti.com/product/bq76pl455a-q1">BQ76PL455A-Q1</a>, <a href="http://www.ti.com/product/bq78350-r1">BQ78350-R1</a>, <a href="https://www.ti.com/product/BQ76942">BQ76952</a></p>
</td>
</tr>
</tbody>
</table>
<p style="text-align:center;"><b> </b></p>
<p align="center" style="text-align:center;"><b>Table 1: Application specific monitoring and protection devices</b><b> </b></p>
<p>If you’re looking to start balancing your battery’s cells, Table 1 matches the perfect monitoring and protection device with your application. If your application is not included in this table or you have questions about your current design, connect with a TI battery expert on the <a href="/support/power_management/battery_management/f/1002" target="_blank">TI E2E battery management forum</a>. </p>
<p><b>Additional resources: </b></p>
<ul>
<li>Get more information on all of TI’s battery management products at <a href="http://www.ti.com/battery" target="_blank">www.ti.com/battery</a>.<b></b></li>
<li><b>Read the blog: </b><a href="/blogs_/b/behind_the_wheel/archive/2015/12/10/from-millivolt-to-miles-how-the-performance-of-battery-management-ics-affects-the-performance-of-the-car-i-drive" target="_blank">From millivolts to miles: How the performance of battery-management ICs affects your car’s performance</a><b></b></li>
</ul><div style="clear:both;"></div><img src="https://e2e.ti.com/aggbug?PostID=668833&AppID=940&AppType=Weblog&ContentType=0" width="1" height="1">Miguel Angel Rioshttps://e2e.ti.com:443/members/3449690How to ensure battery gauge accuracy with BqStudiohttps://e2e.ti.com/blogs_/archives/b/fullycharged/posts/how-accurate-is-your-gauge-part-12016-09-26T20:22:00Z2016-09-26T20:22:00Z<div><b>Other Parts Discussed in Post: </b><a href="https://www.ti.com/tool/BQSTUDIO" class="internal-link folder tool" title="Link to Tool Folder" target="_blank">BQSTUDIO</a></div><div class="WordSection1">
<p align="center"><img src="/resized-image/__size/500x0/__key/communityserver-blogs-components-weblogfiles/00-00-00-09-40/4540.gauge2.jpg" alt=" " /></p>
<p><b>Part 1: Measurement and gauging accuracy</b></p>
<p>A battery gauge, commonly called a gas or fuel gauge, obtains data from the battery to determine how much juice is left in it. Gauging accuracy should not be misconstrued for measurement accuracy of a gauge. The ability of a gauge to accurately report the state of charge and predict the remaining battery capacity depends on various measurements, which may include voltage, current flow and battery temperature. It should be noted that measurement accuracy depends on the gauge’s hardware, while gauging accuracy depends on the robustness of the gauging algorithm and the gauge’s measurement accuracy.</p>
<p>There are three predominant approaches used for battery gauging. The first is to use a voltage look-up table, which is suitable in applications with very light loads. The second is to coulomb-count the charge flowing out of or into the battery (i.e integrate the current into or out of the battery with respect to time), which is a more reliable approach but does have some initialization issues upon battery insertion, i.e knowing what the initial state of charge is. The third method combines the voltage look-up method and coulomb-counting approaches. The accuracy of these gauging methods increases with the complexity of the algorithm, with the voltage look-up method being the least accurate.</p>
<p>Regardless of whatever algorithm you implement to track a battery’s state of charge, because the input variables into the algorithm are the measured values, the accuracy of the measured parameters is critical. Accurate voltage measurement is necessary for initial SOC estimates of a newly inserted battery. This helps account for self-discharge of the battery, given that the self-discharge currents (leakage currents) do not flow through the gauges sense resistor, thus the coulomb counter will be unable to capture these leakage currents. It also aids the correction of accumulated error due to the drift of the sense resistor and errors from the analog to digital converter (ADC) used for coulomb-counting. Accurate current measurement is critical to capture low sleep currents and short load spikes as well as to properly coulomb-count the passed charge. Accurate temperature measurement is critical for proper compensation of calculated battery resistance and capacity due to changes in temperature. All TI devices use one ADC for both voltage and temperature measurements, which is a 15-bit ADC and a separate 15-bit integrating ADC for coulomb counting.</p>
<p>To determine if a gauge is accurately reporting the state of charge of a battery, start with a properly configured gauge and, calibrate the voltage, current and temperature measurements to ensure measurement accuracy. Then you’ll need a way to log the voltage, current and temperature at periodic intervals (one to 10 seconds) for further processing. You can use <a href="http://www.ti.com/tool/BQSTUDIO?keyMatch=bqstudio&tisearch=Search-EN-Everything" target="_blank">TI’s Battery Management Studio (bqStudio)</a> if using a TI gauge to log these measurements, or an Arbin or Maccor which are equipment used for charging and discharging batteries with logging capability. The cells need to be charged to full at room temperature and then discharged to the battery’s terminate voltage using the desired load. <a href="http://www.ti.com/tool/bq27gdk000evm" target="_blank">TI’s gauge development kit</a> (GDK) is a hardware tool that can help automate charge and discharge cycles of the battery when used with bqStudio.</p>
<p>To evaluate gauging accuracy quickly, simply plot the voltage, state of charge and current and conduct a simple inspection to see if 0% SOC is reported near the true battery’s terminate voltage and whether the SOC is smooth without large jumps. Figure 1 shows a graph where the gauge reports 0% SOC near the terminate voltage. The SOC smoothly transitions without large jumps (this was with a constant current load). This approach, although simple, is very subjective and difficult to gauge relative error magnitude. In the sequel blog to this, a more elaborate approach will be discussed which allows a user to guage relative error magnitude.</p>
<p style="text-align:center;"><img src="/resized-image/__size/1230x0/__key/communityserver-blogs-components-weblogfiles/00-00-00-09-40/chart.PNG" alt=" " /></p>
<p align="center"><b>Figure 1: Graph of State of Charge and Voltage against Time</b></p>
<p>In conclusion, it is important that a gauge has excellent measurement accuracy to ensure good gauging accuracy, given that the former is one of the critical requirements to ensure a gauge is correctly reporting the state of charge of a battery. The gauging algorithm employed is another key factor to ensuring good gauging accuracy. Simple inspection of the plotted state of charge and voltage against time is a quick way to determine gauging accuracy. A more elaborate method for determining a gauges accuracy as well as other considerations affecting gauging accuracy will be discussed in <a href="/blogs_/b/fullycharged/archive/2016/11/04/how-accurate-is-your-battery-fuel-gauge-part-2-2" target="_blank">part 2</a> of this blog post.</p>
<p><b>Additional resources: </b></p>
<ul>
<li>Read more blogs on gauging:
<ul>
<li><a href="/blogs_/b/fullycharged/archive/2016/03/11/configuring-a-fuel-gauge-by-reading-the-label-on-the-back-of-your-battery" target="_blank">Configuring a battery fuel gauge by reading the label on the back of your battery</a></li>
<li><a href="/blogs_/b/fullycharged/archive/2016/05/26/where-should-i-place-my-battery_1920_s-gas-gauge" target="_blank">Where should I place my battery’s gas gauge?</a></li>
<li>Learn more about <a href="http://www.ti.com/lsds/ti/power-management/battery-fuel-gauge-tools-software.page?DCMP=bms&HQS=gauge" target="_blank">TI’s battery fuel gauging portfolio.</a></li>
</ul>
</li>
</ul>
<p></p>
</div>
<p> </p><div style="clear:both;"></div><img src="https://e2e.ti.com/aggbug?PostID=669049&AppID=940&AppType=Weblog&ContentType=0" width="1" height="1">Onyx Ahiakwohttps://e2e.ti.com:443/members/1864200Understanding battery charger features and charging topologieshttps://e2e.ti.com/blogs_/archives/b/fullycharged/posts/understanding-battery-charger-features-and-charging-topologies2016-09-19T16:05:53Z2016-09-19T16:05:53Z<p><span style="font-family:inherit;font-size:inherit;">In my previous blog “<a href="http://e2e.ti.com/blogs_/b/fullycharged/archive/2016/07/13/selecting-the-right-battery-charger-for-industrial-applications" target="_blank">Selecting the right battery charger for industrial applications</a><b>”, </b>we discussed the standalone vs. host controlled chargers and external vs integrated switching FETs. Now let’s take a look at different charging topologies.</span></p>
<p><span style="font-family:inherit;font-size:inherit;">First of</span> all, we have to better understand the battery charger features, Dynamic Power Management (DPM) and Dynamic Power Path Management (DPPM). These two features are closely related to charging topology and are equally important. The different topologies determine the DPM and DPPM capability as well as the total cost associated with different components selected. For low power applications, NVDC charger has generated a lot interests for its lower cost and DPM/DPPM features. For higher power applications, the traditional charging topology is selected to minimize the power loss.</p>
<p>Adapters with higher output ratings are generally more expensive. To reduce costs, you may want to use a lower-rated adapter, but doing so requires a charger with a current-based dynamic power management (DPM) function to prevent adapter overload. This protection is in place in case the combined system load and battery load exceed the total power that the adapter can provide. For example, chargers with current based DPM such as the <a href="http://www.ti.com/product/bq24133" target="_blank">bq24133</a> can handle wide input power sources without overloading (Figure 1).</p>
<p align="center"><a href="/cfs-file/__key/communityserver-blogs-components-weblogfiles/00-00-00-09-40/4010.fig1.png"><img src="/resized-image/__size/500x0/__key/communityserver-blogs-components-weblogfiles/00-00-00-09-40/4010.fig1.png" alt=" " /></a></p>
<p align="center"><b>Figure 1: Current-based DPM</b></p>
<p>For peak system performance, you will also need a dynamic power path management (DPPM) function so that the charger can work in supplement mode, which enables the battery to provide power to the system through the battery FET instead of having to be charged (Figure 2). You should consider the trade-off between performance and cost during the design.Higher performance is normally associated with higher cost. A charger controller such as TI’s <a href="http://www.ti.com/product/bq24610" target="_blank">bq24610</a> has both DPM and DPPM control that can support up to 10A charging current.</p>
<p align="center"><a href="/cfs-file/__key/communityserver-blogs-components-weblogfiles/00-00-00-09-40/2671.fig2.png"><img src="/resized-image/__size/500x0/__key/communityserver-blogs-components-weblogfiles/00-00-00-09-40/2671.fig2.png" alt=" " /></a></p>
<p align="center"><b>Figure 2: An example of DPPM Current Path</b></p>
<p>With better understanding on the DPM and DPPM, we can then looking into charging topology. The three most common charging topologies are <b>traditional, hybrid and narrow V<sub>DC</sub> (NVDC)</b>.</p>
<p><b>Traditional topology</b> chargers such as the <a href="http://www.ti.com/product/BQ24170" target="_blank">bq24170</a>, synchronous switch-mode stand-alone battery charger and the <a href="http://www.ti.com/product/BQ24725A" target="_blank">bq24725A SMBus charge controller,</a> the system rail can go as high as the maximum adapter voltage. If operating from the battery, the system voltage can go as low as the minimum battery voltage. A high-voltage input source can cause a wide swing on the system rail (Figure 3). The benefit of using this topology is the system gets maximum power from input source. The downside of this is that the total solution cost is high since the components need to handle high power and are more expensive.</p>
<p align="center"><a href="/cfs-file/__key/communityserver-blogs-components-weblogfiles/00-00-00-09-40/5305.fig3.png"><img src="/resized-image/__size/500x0/__key/communityserver-blogs-components-weblogfiles/00-00-00-09-40/5305.fig3.png" alt=" " /></a></p>
<p align="center"><b>Figure 3: Traditional charging topology</b></p>
<p>In some applications, the system only requires peak power delivery. An adapter designed for normal operation cannot meet peak power requirements, and a traditional charging topology does not allow batteries to work in supplement mode to provide additional power. The solution is a <b>hybrid charging topology</b>, as shown in Figure 4.</p>
<p align="center"><a href="/cfs-file/__key/communityserver-blogs-components-weblogfiles/00-00-00-09-40/7462.fig4.png"><img src="/resized-image/__size/500x0/__key/communityserver-blogs-components-weblogfiles/00-00-00-09-40/7462.fig4.png" alt=" " /></a></p>
<p align="center"><b>Figure 4: Hybrid charging topology</b></p>
<p>In a hybrid charging topology, the battery can provide additional power to the system in boost mode for peak power delivery. Devices such as the <a href="http://www.ti.com/product/bq24735" target="_blank">bq24735</a> and <a href="http://www.ti.com/product/bq24780s" target="_blank">bq24780S</a> battery charger ICs fall into this category. The hybrid charging topology is also called “turbo boost” mode. This topology is very popular in laptop applications.</p>
<p>Both traditional and hybrid charging topologies require the system rail to handle a high voltage at the same level as the input source. However, in some applications, the system rail needs to have lower rating components to reduce the cost. In such cases, consider an <b>NVDC topology</b> included in such products as the <a href="http://www.ti.com/product/bq24770" target="_blank">bq24770</a> or <a href="http://www.ti.com/product/bq24773" target="_blank">bq24773</a> to align the system voltage very closely to the battery voltage by controlling the battery FET, as shown in Figure 5.</p>
<p align="center"><a href="/cfs-file/__key/communityserver-blogs-components-weblogfiles/00-00-00-09-40/0537.fig5.png"><img src="/resized-image/__size/500x0/__key/communityserver-blogs-components-weblogfiles/00-00-00-09-40/0537.fig5.png" alt=" " /></a></p>
<p align="center"><b>Figure 5: NVDC charging topology</b></p>
<p>When designing a charging system, the balance among performance, features and solution cost has to be balanced. Choosing the right topology and device can achieve higher efficiency while maintain the lowest solution cost. For more information on choosing the right battery charger for your design, please visit the <a href="http://www.ti.com/lsds/ti/power-management/battery-charger-ic-overview.page" target="_blank">battery charger solutions page</a>.</p>
<p>Additional resources:</p>
<ul>
<li>Read my last blog post: <a href="/blogs_/b/fullycharged/archive/2016/07/13/selecting-the-right-battery-charger-for-industrial-applications" target="_blank">Selecting the right battery charger for industrial applications</a></li>
</ul><div style="clear:both;"></div><img src="https://e2e.ti.com/aggbug?PostID=669025&AppID=940&AppType=Weblog&ContentType=0" width="1" height="1">Ming Yuhttps://e2e.ti.com:443/members/285113Pass your power bank EMI testhttps://e2e.ti.com/blogs_/archives/b/fullycharged/posts/pass-your-power-bank-emi-test2016-08-24T21:29:00Z2016-08-24T21:29:00Z<p align="center"><img src="/resized-image/__size/500x0/__key/communityserver-blogs-components-weblogfiles/00-00-00-09-40/power-bank.jpeg" alt=" " /> </p>
<p>A key design challenge when designing a power bank is passing the electromagnetic interference (EMI) test. Electronics engineers often fear EMI test failures, and it would be a nightmare if the circuit failed the EMI test again and again. You would have to work day and night in the lab to fix the problem to avoid product launch delays. For consumer products like power banks, the design period is short, while the EMI certification limit is strict. So you want to add enough EMI filters to pass the EMI test smoothly, but you also don’t want to increase space or add much cost to the circuit. It seems hard to achieve both.</p>
<p>The <a href="http://www.ti.com/lit/ug/tidubt9/tidubt9.pdf" target="_blank">Low Radiated EMI Boost Converter Reference Design</a> provides such a solution. It can support a 2.7V-4.4V input voltage, 5V/3A, 9V/2A and 12V/1.5A output power, making it fit for the power bank applications. By optimizing the placement and layout, this reference design can get higher than 6dB margin in EN 55022 and International Special Committee on Radio Interference (CISPR) 22 Class-B radiation tests. Let’s take a look at the design process.</p>
<p class="HdrNumh1"><strong> </strong></p>
<p><b>Identify the critical current path</b></p>
<p>EMI starts off from the high instantaneous rate of current change (di/dt) loops. So you should differentiate the high di/dt critical path at the beginning of your design. It is important to understand the current conduction paths and signal flows in the switching power supply.</p>
<p>Figure 1 shows the topology and critical current path of the boost converter. When S2 closes and S1 opens, AC current flows through the blue loop. When S1 closes and S2 opens, AC current flows through the green loop. So the current flow through input capacitor Cin and inductor L is a continuous current, while the current flow through S2, S1 and the output capacitor Cout is a pulsating current (red loop). The red loop is thus the critical current path. This path has the highest EMI energy. You should minimize the area enclosed by it during layout.</p>
<p class="para" align="center" style="text-align:center;"><img src="/resized-image/__size/1230x0/__key/communityserver-blogs-components-weblogfiles/00-00-00-09-40/0310.fig1.PNG" alt=" " /></p>
<p align="center"><b>Figure 1: Critical current path of boost converter</b></p>
<p style="text-align:center;"><strong style="text-align:left;">Minimize High di/dt Path Loop Area</strong></p>
<p>Figure 2 shows the pin configuration of the <a href="http://www.ti.com/product/tps61088" target="_blank">TPS61088</a>. Figure 3 shows the <a href="http://www.ti.com/product/tps61088" target="_blank">TPS61088</a> critical current path layout example. The NC pin means that there is no connection inside the device, so it can be connected to PGND. From an electrical point of view, connecting the two NC pins to the PGND ground plane is good for thermal dissipation and can reduce the impedance of the return path. From an EMI point of view, connecting two NC pins to the PGND ground plane makes the VOUT and PGND plane of the <a href="http://www.ti.com/product/tps61088" target="_blank">TPS61088</a> much closer to each other. And that makes the placement of the output capacitors much easier.</p>
<p>From Figure 3, you can see that placing one 0603 1µF (or 0402 1µF) high-frequency ceramic capacitor C<sub>OUT_HF</sub> as close to the VOUT pin as possible results in a minimum area of the high di/dt loop.</p>
<p class="para" align="center"><a href="/cfs-file/__key/communityserver-blogs-components-weblogfiles/00-00-00-09-40/2476.fig2.PNG"><img src="/resized-image/__size/1230x0/__key/communityserver-blogs-components-weblogfiles/00-00-00-09-40/2476.fig2.PNG" alt=" " /></a></p>
<p align="center"><b>Figure 2: </b><a href="http://www.ti.com/product/TPS61088" target="_blank" title="Link to Product Folder"><b>TPS61088</b></a><b> pin configuration</b></p>
<p class="para" align="center"><a href="/cfs-file/__key/communityserver-blogs-components-weblogfiles/00-00-00-09-40/5100.fig3.PNG"><img src="/resized-image/__size/1230x0/__key/communityserver-blogs-components-weblogfiles/00-00-00-09-40/5100.fig3.PNG" alt=" " /></a></p>
<p align="center"><b>Figure 3: </b><a href="http://www.ti.com/product/TPS61088" target="_blank" title="Link to Product Folder"><b>TPS61088</b></a><b> critical path layout example</b></p>
<p>Equation 1 calculates the maximum electric field strength from such a high di/di loop over a ground plane at a 10m distance:</p>
<p class="para" style="text-align:center;"><img src="/resized-image/__size/1230x0/__key/communityserver-blogs-components-weblogfiles/00-00-00-09-40/equation.PNG" alt=" " /></p>
<p class="para">Where A is the loop area, <a href="/cfs-file/__key/communityserver-blogs-components-weblogfiles/00-00-00-09-40/4744.2.PNG"><img src="/resized-image/__size/1230x0/__key/communityserver-blogs-components-weblogfiles/00-00-00-09-40/4744.2.PNG" alt=" " /></a><i> </i>is the current flowing in the loop, <a href="/cfs-file/__key/communityserver-blogs-components-weblogfiles/00-00-00-09-40/f.PNG"><img src="/resized-image/__size/1230x0/__key/communityserver-blogs-components-weblogfiles/00-00-00-09-40/f.PNG" alt=" " /></a><i> </i> is the interested frequency of . So smaller critical path area means smaller radiation energy.</p>
<p class="para"><i> </i></p>
<p class="para">Figure 4 shows the radiated EMI result with and without C<sub>OUT_HF</sub>. Under the same test condition, the radiated EMI is improved by 4dBuV/m with C<sub>OUT_HF</sub>.</p>
<p class="para" align="center"><a href="/cfs-file/__key/communityserver-blogs-components-weblogfiles/00-00-00-09-40/7266.fig4.PNG"><img src="/resized-image/__size/1230x0/__key/communityserver-blogs-components-weblogfiles/00-00-00-09-40/7266.fig4.PNG" alt=" " /></a> </p>
<p align="center"><b>Figure 4: Radiated EMI result with and without C</b><b><sub>OUT_HF</sub></b></p>
<p><b>Putting a ground plane under the critical path</b></p>
<p>High trace inductance leads to poor radiation EMI because the magnetic field strength is in direct proportion to the inductance. Placing a solid ground plane on the next layer of the critical trace can solve this problem.</p>
<p>Table 1 gives the inductance of a given trace on different printed circuit board (PCB) boards. You can see that for a four-layer PCB with a 0.4mm insulation thickness between the signal layer and the ground plane, the trace inductance is much smaller than that of a 1.2mm-thick two-layer PCB. So putting a solid ground plane with a minimum distance to the critical path is one of the most effective ways to reduce EMI.</p>
<p align="center" style="text-align:left;"><strong>Table 1. Trace inductance (trace length = 5cm)</strong></p>
<div align="right" style="text-align:left;">
<table border="1" cellspacing="0" cellpadding="0" style="width:638px;">
<tbody>
<tr>
<td width="118" valign="top">
<p class="TableOLhdr">PCB</p>
</td>
<td width="140" valign="top">
<p class="TableOLhdr">h (mm)</p>
</td>
<td width="138" valign="top">
<p class="TableOLhdr">W<sub>g</sub>(mm)</p>
</td>
<td width="242" valign="top">
<p class="TableOLhdr">L(nH)</p>
</td>
</tr>
<tr>
<td width="118" valign="top">
<p class="TableOLhdr">Single-Layer PCB</p>
</td>
<td width="140" valign="top">
<p class="TableOLcenter"><b>--</b></p>
</td>
<td width="138" valign="top">
<p class="TableOLcenter"><b>--</b></p>
</td>
<td width="242" valign="top">
<p class="TableOLcenter"><b>52</b></p>
</td>
</tr>
<tr>
<td width="118" valign="top">
<p class="TableOLhdr">2-Layer PCB</p>
</td>
<td width="140" valign="top">
<p class="TableOLcenter"><b>1.2</b></p>
</td>
<td width="138" valign="top">
<p class="TableOLcenter"><b>10</b></p>
</td>
<td width="242" valign="top">
<p class="TableOLcenter"><b>3.6</b></p>
</td>
</tr>
<tr>
<td width="118" valign="top">
<p class="TableOLhdr">4-Layer PCB</p>
</td>
<td width="140" valign="top">
<p class="TableOLcenter"><b>0.4</b></p>
</td>
<td width="138" valign="top">
<p class="TableOLcenter"><b>10</b></p>
</td>
<td width="242" valign="top">
<p class="TableOLcenter"><b>1.2</b></p>
</td>
</tr>
</tbody>
</table>
</div>
<p class="para" style="text-align:center;"></p>
<p>Figure 5 shows the radiated EMI result of a two-layer PCB and a four-layer PCB. Under the same layouts and same test conditions, the radiated EMI improves by more than 10dBµV/m with a four-layer PCB.</p>
<p class="para" style="text-align:center;"><b><a href="/cfs-file/__key/communityserver-blogs-components-weblogfiles/00-00-00-09-40/0333.fig5.PNG"><img src="/resized-image/__size/1230x0/__key/communityserver-blogs-components-weblogfiles/00-00-00-09-40/0333.fig5.PNG" alt=" " /></a></b><b> </b><b> </b></p>
<p align="center"><b>Figure 5: Radiated EMI result of a two-layer PCB and a four-layer PCB</b></p>
<p class="para" align="center" style="text-align:left;"><strong>Adding RC snubber</strong></p>
<p>If the radiation level still exceeds the requirement level and the layout cannot be improved anymore, then adding a resistor-capacitor (RC) snubber across the <a href="http://www.ti.com/product/tps61088" target="_blank">TPS61088</a>’s switch pin and the power ground can help reduce radiation EMI levels. The RC snubber should be as close as possible to the switching node and the power ground (Figure 6) to effectively damp out switch voltage ringing, which means that you can improve radiated EMI at the ringing frequency.</p>
<p></p>
<p class="para" align="center"><a href="/cfs-file/__key/communityserver-blogs-components-weblogfiles/00-00-00-09-40/3056.fig6.PNG"><img src="/resized-image/__size/1230x0/__key/communityserver-blogs-components-weblogfiles/00-00-00-09-40/3056.fig6.PNG" alt=" " /></a></p>
<p align="center"><strong>Figure 6. Placement of RC snubber</strong></p>
<p>With these simple yet effective optimizations, good EMI performance is possible in power bank designs. Start your design process now by downloading the boost converter reference design. This design is also fit for <i>Bluetooth</i>® speakers, portable point-of-sale (POS) terminals and more.</p>
<p><b>Additional resources</b></p>
<ul>
<li>Read more <span style="text-decoration:underline;"><a href="/search?q=power%20banks&tag=power%20banks" target="_blank">blog posts about power banks</a></span>.</li>
</ul><div style="clear:both;"></div><img src="https://e2e.ti.com/aggbug?PostID=668938&AppID=940&AppType=Weblog&ContentType=0" width="1" height="1">Helen chenhttps://e2e.ti.com:443/members/4197150Join the wireless power LinkedIn chathttps://e2e.ti.com/blogs_/archives/b/fullycharged/posts/linkedin-chat-blog2016-08-22T16:03:00Z2016-08-22T16:03:00Z<p align="center" style="text-align:left;"><span style="font-family:inherit;font-size:inherit;">Want to learn more about wireless power? Bring your questions to our expert panel as IEEE, TI and the Wireless Power Consortium (WPC) team up to host a <b style="font-size:12px;">free</b> live Q&A on the IEEE Power Electronics Society LinkedIn Group. Request to join the group <a href="https://www.linkedin.com/groups/2091456/profile" target="_blank">here</a> ahead of time and tune in on August 30, 2016 from 9:00-10:00 a.m. CT to chat about what wireless power looks like today and how it’s being adopted in emerging sectors like industrial and automotive. Whether you are searching for insight on the latest trends or designing your own products, our gurus are here to chat! </span></p>
<p style="text-align:left;"><span style="font-family:inherit;font-size:inherit;">The free live Q&A will feature IEEE, TI</span> wireless power experts Janice Escobar and Dick Stacey and WPC expert, John Perzow. Learn more about them below!</p>
<p>RSVP to our Facebook event here and invite your friends! And be sure to request access to the <a href="https://www.linkedin.com/groups/2091456/profile" target="_blank">LinkedIn group</a> to participate. We look forward to seeing you on the IEEE PELS group soon! </p>
<p align="center"><b>Meet the wireless power experts</b></p>
<p align="center"><img src="/resized-image/__size/600x0/__key/communityserver-blogs-components-weblogfiles/00-00-00-09-40/Dick-Stacey.jpg" alt=" " /></p>
<p><strong>Dick Stacey</strong> graduated from The University of Texas with a BSEE. He joined TI when Benchmarq was acquired in 1999 and has worked in various roles including test, systems, applications and validation. Dick has worked on products ranging from load switches to LED drivers and a variety of battery products from chargers to battery fuel gauges, now focusing on applications in the wireless power group. </p>
<p style="text-align:center;"><img src="/resized-image/__size/350x0/__key/communityserver-blogs-components-weblogfiles/00-00-00-09-40/2806.Escobar_5F00_Janice.jpg" alt=" " /></p>
<p><strong>Janice Escobar</strong> graduated from Lehigh University with a degree in computer engineering. She joined TI as an application rotation employee and has recently moved to product marketing after three years at Texas Instruments. Janice has worked on products including power management ICs to smart grid technologies and is now focusing on wireless power. </p>
<p style="text-align:center;"> <img src="/resized-image/__size/500x0/__key/communityserver-blogs-components-weblogfiles/00-00-00-09-40/John-Perzow.jpg" alt=" " /></p>
<p><b>John Perzow</b> is the vice president, market development for the <a href="http://www.wirelesspowerconsortium.com/">Wireless Power Consortium</a> and founder, <a href="http://www.asmconsultantsllc.com/">ASM Consultants, LLC</a>, which provides market research, product, market and corporate development consulting services for analog and mixed-signal semiconductor and system manufacturers.</p>
<p>Prior to founding his consulting group, John was the marketing director for Analog Devices Power Management group, the marketing director and product line manager for the power group of Broadcom Corp. and marketing director for National Semiconductor power group. John began his career as part of the start-up team of Comlinear Corporation, which designed high-speed amplifiers and data converters. He holds a BS in Electrical Engineering Education from Colorado State University and an MBA from the University of Colorado. John is co-named in six patents in power electronic circuit design and is on the Industrial Advisory Board, Colorado State University. John and his wife reside in Fort Collins, Colorado.<b></b></p>
<p></p><div style="clear:both;"></div><img src="https://e2e.ti.com/aggbug?PostID=668942&AppID=940&AppType=Weblog&ContentType=0" width="1" height="1">Katie Worthyhttps://e2e.ti.com:443/members/4150604