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Zoom™ AM1808 EVM - PMIC battery charging issue

Filosofi
Intellectual 925 points
Other Parts Discussed in Thread: TPS65070, AM1808

Hi all,

I'm doing some tests powering the system with a 180mAh single cell Li-ion battery (3.6V nominal voltage).

 

I've connected the positive terminal of the battery to the MAIN_BATT_IN pin of the SOM-M1 module, and the negative one to GND (in brief across C47).

 

When the system is on (running u-boot) and I unplug the 5V power cord, correctly the TPS65070 PMIC switches onto the battery supply and the system still remains on.

 

The problem arised when I tested the charging capability of the PMIC.

 

I read the TPS65070 PMIC is capable of charging the battery from the 5V input, but I was not able to see any charging current, even with the battery voltage as low as 2V.

 

Did anybody successfully charge a battery with such a system ?

Does anybody knows if there any SW/HW settings I've not considered yet ?

The Zoom™ AM1808 EVM is 1015525 Rev 2

The SOM-M1 is SOMAM1808-10-1502QHCR-A (1016966)

 

Best regards,

 

Gabriele

 

  • 0
    Intellectual 925 points

    Hi all,

    FYI

    the problem was dua to the NTC monitor within PMIC TPS65070. This engine prevents any charging activity because the TS input of the PMIC was floating. I solved by placing a 10kohm resistor pull-down on EVM baseboard, R92. Tis resistor is not populated on the EVM as it is. So, with a 10kohm resistor you can simulate the safe value of a NTC thermistor, and the charging activity takes pace when needed. The best would be, of course, to use a real NTC thermistor!

     

  • 0 in reply to Filosofi
    Prodigy 30 points

    Gabriel

    Please also note the following:

    To cause failure:
       1) Power system on battery only. Run until UVLO causes power-down.
       2) Battery voltage recovers somewhat because system load is removed.
       3) Press PB_IN to attempt power-on. power-on doesn't succeed because battery voltage immediately collapses.
       4) Though power-on is not successful (core and I/O regulators are at 0V), VSYS is on, master reset is held low by PMIC.

    The chosen fix was to remove pull-up resistor R166. This has two effects:
       1) The system no longer powers on immediately when USB power is present. PB_IN must be pressed to turn the system on, regardless of the power source.
       2) The processor is now required to directly drive POWER_ON high to keep the system on. If PB_IN is released before POWER_ON is high, the system will power down immediately.

     

    Nate