DC/DC WITH LIGHT LOAD

Hi Eli,

I think either the TPS54040 or the TPS62170 could be a good fit.

The TPS54040 gets pretty close to your 100uA target. It draws 116uA of quiescent current at light load.

TPS54040:

• 3.5V to 42V Input Voltage Range
• 200-m High-Side MOSFET
• High Efficiency at Light Loads with a Pulse Skipping Eco-Mode™
• 116µA Operating Quiescent Current
• 1.3µA Shutdown Current
• 100kHz to 2.5MHz Switching Frequency
• Synchronizes to External Clock
• Adjustable Slow Start/Sequencing
• UV and OV Power Good Output
• Adjustable UVLO Voltage and Hysteresis
• 0.8-V Internal Voltage Reference

Your other option is the TPS62170. It exceeds your 100uA target but the Vin max is 17V.

TPS62170:

• DCS-Control^TM Topology
• Input Voltage Range: 3 to 17 V
• Up to 500mA Output Current
• Adjustable Output Voltage from 0.9 to 6 V
• Fixed Output Voltage Versions
• Seamless Power Save Mode Transition
• Typically 17µA Quiescent Current
• Power Good Output
• 100% Duty Cycle Mode
• Short Circuit Protection
• Over Temperature Protection

Hope this helps.

Regards

Stephen Ott

Eli,

It would be good to know what input source you have that is driving the very wide Vin range?

Your local contact (Ofer I believe) should be in contact with you shortly about this design.  The two devices mentioned are both options for you.

As we discussed previously, the TPS5404 would work, but at extremely low loads, efficiency will be in the 25-35% range.

Hi,

Application is motion control unit for solar panels.

1. As John indicated,TPS54040,is not good as it will give only 25%-35%.Customer need 50% minimum

2.The new TPS62175,will not workede,ae its Vin mini. is from 4.7V. Customer need from 4.00V

3.What will be the efficiancy of the TPS62170 at 200UA load?

B.regards

Eli

Are the solar panels the input source?  We need to know what is driving the extremely wide range of your Vin.  Such a wide range leads to a non-optimized solution for you.  Your local FAE can discuss this in more detail with you but know that TI offers a much more cost competitive solution than LT, if you are able to loosen your specs (Vin range or efficiency need) just a little bit.

The TPS62170 efficiency data can be found in the datasheet.

Hi,

The source for the power are super caps which are charged up to 17.6V  max charging of these capacitors is 18V (they are only charged to 17.6 in order to extend life time).

The lower voltage is set due to the fact that they are discharged down to this level and on that level they should be sufficient to power up 3.3V circuitry.

This is good to know your input source and that the 18V and 4V are arbitrary numbers corresponding to a certain amount of hold up energy for your system.  In this case, I would recommend changing to a 3.4V or 3.5V to 17V storage voltage range and using the TPS62150.  This device has lower Rds-on FETs and so can keep the 3.3V output regulated down to lower Vins--allowing you to get the most energy out of your input cap.

We also have the TPS62125 releasing soon.  It is more efficient than the TPS62150 at very light loads.  Check back later this week on ti.com for more information.

Hi,

You might also want to look at the LM26001.  It has a very low IQ and an input voltage range that meets your customers specifications.

LM26001Q is an Automotive Grade product that is AECQ100

grade 1 qualified (-40°C to +125°C operating

junction temperature)

■ High efficiency sleep mode

■ 40 μA typical Iq in sleep mode

■ 10 μA typical Iq in shutdown mode

■ 3.0V minimum input voltage

■ 4.0V to 38V continuous input range

The datasheet does not show the efficiency at 100uA, but If this looks like it might work for you I can ask a tech to order a board and measure the efficiency.

http://www.ti.com/lit/ds/symlink/lm26001.pdf

Hi,

But the Vin max for TPS62150 is 17V,whillneeded is 18V.

Is the tPS62155 will have wider Vin than 17V?

What about screening option for 18V?

B.regards

Eli

Hi Marc,

Thanks. I got the below feedback on thios device from Allan Fisher:

"I don’t have the data. But if the output power is 330uW, and the input is 18V, and the efficiency is 50%....

That gives an input current = 37uA.

This is lower than the typical IQ in sleep mode. It does not include all the contributors to input current, primarily load current and gate charge during bursting.

That tells me that we can’t meet the spec with the LM26001"

If you think its should work,please test and advise.

Eli,

You stated in your last post that you only needed 17.6V.  I replied that possibly you could get by with 17V since you can go further down in voltage on the lower end--down to 3.4V potentially and still keep the 3.3V in regulation.  This might allow you to get the same energy out of your supercap.

The TPS621xx parts will operate at 18V, but it is above the recommended range.  It is not a matter of screening but simply that the part was not characterized at that input voltage.  So, we cannot recommend using it there.

You will need to look into your system specs and see what the best part is for you.  We have recommended several devices in this thread, each with their own tradeoffs of size, efficiency, cost, etc.  Your requirements are very challenging and it is very possible that no cost effective solution is currently present in the market that meets the entirety of your specs.  The LT part you mentioned only operates down to 4.2V and I would argue that it is not a cost effective solution, especially compared to the other devices we have recommended here.  Your local TI FAE can help you select the right device that best meets your needs.