TPS61030: TPS61030RSAR IC power booster chip

Awesome. I look forward to hearing from them! Thanks for getting back to me so soon. 

Dear Jasper Li,

Do you mean the PCB schematic layout? There should be three pictures attached to my question, the first one being my PCB schematic layout pertaining to the power booster circuit. The last picture is your web-site's simulated circuit based off the second picture's input. Also notice that I then explain, that I changed the values for some of the chips, around the power booster schematic, which is giving the results I'm sharing with you. 

Yes it seems that when the DC voltage, Vin, from a 5 Ah, 4.2 V (charged) to 3 V (dead) Li-ion battery, goes below 3.7 V it struggles to give the Vout enough current to run the system. My system requires 1.2 to 1.25 A to function fully. 

I would ideally like to know what chips values I need to change to enable the power booster IC chip to be able to produce more than enough current to power my system. Does that make sense?

--

Kai 

Vin (yellow) and Vout (purple) waveforms:

The layout was created by an expert that has over 50 years experience. I'm a student and my job is designing the schematic, he creates the PCB files from my schematic and designs the layout so I'm sure the layout is correct. I don't have the layout files with me but I can ask him for them, if you really think that is the concern. 

Best

Kai

Yes I will assemble another board this week when the parts arrive. 

Also I want to double check with you that you're sure that, that power booster can support 1.3 A at 5.2 V from 3 V.

It occurred to me that the amount of input current I need depends on the ratio of output voltage to the input voltage.

Over the long term, boost conveters are constant-power devices with some loss: to get 1.3A @ 5V out (6.5W), an ideal boost converter would need 1.76A @ 3.7V of input (also 6.5W). No converter is 100% efficient though, and at 90% efficiency you need 1.95A @ 3.7V of input (6.5W + 650mW loss).

If you drop the input voltage to 3.3V, the current has to rise to about 2.2A. Right? 

Over the short term, boost converters are constant-current devices whose long-term input and output currents are chopped by PWM, with the PWM duty cycle based on the ratio of the input voltage to the output voltage. 5.2V/3.7V=1.4, so an ideal boost converter's duty cycle would be 1.4:1 or 58% to 42%. The 1.3A long-term average output current is really a series of 1.3/0.42=3.1A bursts at a 42% duty cycle. The input current is also 3.1A chopped by a 58% duty cycle, or 1.8A. That's an ideal ratio though, and taking the 90% efficiency into account raises the input current to about 1.95A, and 1.95A/0.58=3.4A.

If we drop the input voltage to 3.3V, the ratio becomes 5.2/3.3=1.57, so an ideal converter's duty cycle would be 61% to 39%. The 1.3A output current would become 1.3/0.39=3.33A chopped at a 39% duty cycle, and the input current would be 3.33A chopped at a 61% duty cycle, or 2A. Adjusting for 90% efficiency takes the input current up to 2.2A average, or 3.6A chopped at a 61% duty cycle.

Even those are only approximations of what happens during one boost cycle though. The instantaneous current rises during the input phase and decays during the output phase, with the instantaneous maximum and minimum depending on the inductor and duty cycle. The TPS61030 seems to stay in the region where the rate of change is nearly linear, but the maximum instantaneous current is still a few hundred milliamps higher than the minimum.

The 3.4A and 3.6A average values calculated above are only a few hundred milliamps away from the TPS61030's 4A absolute maximum switching current, so the problem may be that the instantaneous peak is hitting that 4A limit. Is that incorrect? I hope I'm wrong and that you're right because that makes things a lot easier. It just costs money and time to assemble another board, both of which I have little of because I'm a mechanical engineering student and it's finals this week. So it would be nice to know that my schematic defiantly correct before I assemble another board. Please let me know what you think. Thanks so much for your patience! 

Jasper Li,

Okay that's good to know. Thank you! 

It looks like the EVM kit is not available... http://www.ti.com/tool/tps61030evm-208 

I got the schematic idea, for Q1 LED circuit, from Adafruit https://learn.adafruit.com/adafruit-powerboost-1000-basic/downloads 

All the parts are almost here to solder and assemble another board! It sounds like you're saying, that when assembling the board this time, I should use the exact chip values shown in my original schematic? Or should I use a 200 KΩ resistor in place of R4 and a 220 uF capacitor in place of C6? Or other suggestion?

I'm wondering about the values of the chips because my original schematic reflects the Adafruit power boost 500 basic, which is meant to supply only 500 mA  https://learn.adafruit.com/adafruit-powerboost/downloads 

That's why I'm wondering if using the Adafruit power boost 1000 basic schematic is a better choice because it's meant to supply 1000 mA, which is closer to what my circuit demands. The only difference between the two Adafruit schematics is a 200 KΩ resistor and two 100 uF capacitors in parallel, hence the 220 uF capacitor. https://learn.adafruit.com/adafruit-powerboost-1000-basic/downloads

Hopefully that clears things up with my concern about the values of the chips. 

Also below is a view of the circuit layout you asked for. This is looking at it from the bottom side of the PCB. Is this the layout picture you are looking for?

Thanks again for helping me out!

Best regards,

Kai Gull

Jasper Li,

Okay that's good to know. Thank you! 

It looks like the EVM kit is not available... http://www.ti.com/tool/tps61030evm-208 

I got the schematic idea, for Q1 LED circuit, from Adafruit https://learn.adafruit.com/adafruit-powerboost-1000-basic/downloads 

All the parts are almost here to solder and assemble another board! It sounds like you're saying, that when assembling the board this time, I should use the exact chip values shown in my original schematic? Or should I use a 200 KΩ resistor in place of R4 and a 220 uF capacitor in place of C6? Or other suggestion?

I'm wondering about the values of the chips because my original schematic reflects the Adafruit power boost 500 basic, which is meant to supply only 500 mA  https://learn.adafruit.com/adafruit-powerboost/downloads 

That's why I'm wondering if using the Adafruit power boost 1000 basic schematic is a better choice because it's meant to supply 1000 mA, which is closer to what my circuit demands. The only difference between the two Adafruit schematics, is a 200 KΩ resistor and two 100 uF capacitors in parallel, hence the 220 uF capacitor. https://learn.adafruit.com/adafruit-powerboost-1000-basic/downloads

Hopefully that clears things up with my concern about the values of the chips. 

Also below is a view of the circuit layout you asked for. This is looking at it from the bottom side of the PCB. Is this the layout picture you are looking for?

Thanks again for helping me out!

Best regards,

Kai Gull

Dear Jasper Li,

Sorry for the late response! It's been Christmas break and the campus lab is closed, so I had to buy all the tools and set up lab at home. I'll let you know when it's working when it does (:

So to confirm your instructions:

1. Your saying I should find a 100 uF capacitor with an ESR of 50 mOhm, rather than 250 mOhm? Also that I should put two of them in parallel to give a total capacitance of 200 uF? 
   1. Do you recommend to put two of these capacitors in parallel? https://www.digikey.com/product-detail/en/avx-corporation/TCJY107M016R0050/478-9490-1-ND/5001702
   2. Could I instead use this single 220 uF and save over a dollar in cost per board? https://www.digikey.com/product-detail/en/avx-corporation/TCJY227M006R0050/478-9503-1-ND/5001715
   3. Or do you know of a capacitor you could recommend to me?

2. For the Q1 circuit I was clarifying that you noticed that my Q1 transistor is backwards, compared to the Adafruit schematic, as shown below. Is that what you meant?  
   1. My schematic                                 and Adafruit's schematic 
      1. 
   2. Are you saying that I should design that part of the schematic a completely different way or just correct it to the way Adafruit has it?
3. I was able to solder my PCB again using the original chip values in the original schematic, as shown below, to double check if it was a soldering issue.
   1. 
   2. The results where the exact same as before, meaning it was not able to power the entire system when the voltage dropped below 4 V; therefore it was not a soldering issue. Again I want to clarify that changing the capacitor to the 220 uF with the ESR of 2 Ohm (https://www.digikey.com/product-detail/en/avx-corporation/TLJT227M006R2000/478-5989-1-ND/2197011) did allow the system to fully run given over 3.7 V which is better than 4 V.

It seems you are telling me the problem is that the resistance in the capacitor was too large?If you are sure about this I will remanufacture the PCBs with a corrected footprint to fit the new capacitors and also will correct the Q1 circuit. What do you think? 

Best,

Kai

Again the original circuit, now soldered twice, behaves the exact same meaning it is not able to support 1.3 A at 3 V. The voltage has to be at or above 4 V in order for it to support 1.3 A. So I don't know what you mean by "the 2ohm ESR may work for stable application."

Is the reason the circuit can't support 1.3 A as low as 3 V is because the C6 capacitor had a ESR of 2 Ohm rather than 50~100 mOhm? I will order that capacitor now to test it in my circuit, two days shipping. 

Kai

Before you mentioned the below about the PCB layout:

So you're saying pins five though seven should be connected to the thermal pad? The below shows pins five through seven on the IC chip data sheet.

When the data sheet does not show those pins connected the the thermal pad directly as shown below. I'm confused could you please clarify.

Also concerning the original topic before why did you change your mind about the C6 capacitor? Originally you said my schematic looked good with the single 100 uF capacitor, but now you changed your mind saying I need two 100 uF capacitors in parallel or a single 220uF capacitor. Why did you not mention this in the beginning? 

Is there a way I could call and talk over the phone with you or another engineer that specializes in this IC chip?

Kai 

After replacing the C6 capacitor the voltage showed to be 3.5 V output from a 4.2 V input, when it should be 5.175. I then removed the Q1 transistor and that did not effective the voltage. I'm still trying to diagnose why this is happening now.