BQ25616: My Custom PCB performs worse than EVM model

Khoi Ly

Part Number: BQ25616
Other Parts Discussed in Thread: EV2400, TPS61027

Dear TI,

I was successfully make my custom PCB based on the EVM of BQ25616 and it works properly with a Li-ion battery. Thank you Michael Emanuel for superb support!

Currently, I am evaulating the PCB performance and I notice that the current drawn from the same power supply for the EVM was higher than that for my PCB (110 mA vs 87 mA).

I know that the cable length and traces are important factor to the amount of current the charger can deliver to the battery, but I have a very basic questions that I am not entirely understanding.

If the difference between my PCB and the EVM is some traces length and width on VBAT, how could it affects the current drawn so much? especially the wire resistances can be different in the order of 10 mOhm.

Would this be because the internal resistance of LI-ION battery is so small, say 10 mOhm. So my traces that has 10 mOhm larger than the EVM causes the total resistance of the load to be double? Which causes the current to delivered to the battery to be half?

Is there something else fundamental I am missing?

Thank you,

Khoi

6 months ago

+1 Michael Emanuel35 6 months ago

TI__Mastermind 33605 points

Hi Khoi,

Glad you got it to work!

First, are the same conditions being applied? For example, do VBUS, VBAT, etc measure the same voltage?

Second, are the register configurations the same?

Third, depending on the actual voltage on the across the VBAT pin, you could be in CV mode and the charge current is reduced. If the path is longer to the battery in one case vs. the other, the longer path will make it easier to enter CV with a lower charge current.

Regards,

Mike Emanuel

0 Koos Pieterse 5 months ago in reply to Michael Emanuel35

Prodigy 60 points

How do you configure the register?

0 Michael Emanuel35 5 months ago in reply to Koos Pieterse

TI__Mastermind 33605 points

Hello,

You need to use an EV2400 or something capable of making I2C writes to the device.

Regards,

Mike Emanuel

0 Khoi Ly 5 months ago in reply to Michael Emanuel35

Prodigy 240 points

Hi Mike, I realized that I used a wrong boost converter to power the charging circuit. the TPS61027 can only max at 200 mA or so, I think it is the main reason for my slow charging rate. I have redesigned the circuit now and hopefully it will resolve my issue. Thank you for your help.

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BQ25616: My Custom PCB performs worse than EVM model