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BQ25672EVM: Current consumption issue

Andreas Sjöblom
Prodigy 10 points
Part Number: BQ25672EVM
Other Parts Discussed in Thread: BQ25798

Tool/software:

Hello,

I am testing the this BQ25672EVM kit:

I have connected a 4V battery to battery input, I have a solar panel connected to VIN2. All registers are default.

When voltage from solarpanel > 3.6V charging starts as it should but,

when voltage from solarpanel is between 2.5V and 3.6V current drawn from battery is around 400uA. How can I get this down to 20uA?

When solarpanel voltage is below 2.5V current drawn from battery is around 20uA. 

 

Edited: Low current is 20uA not 2uA

  • 0
    TI__Prodigy 330 points

    Hi Andreas,

    For your test setup, do you have another source connected to VIN1 or a load on SYS? When the solar panel drops between 2.5V and 3.6V, are ACFET2-RBFET2 turning off?

    Best Regards,

    Austin

  • 0 in reply to Austin Allen
    Prodigy 10 points

    Hi Austin,

    Thank you for your reply!

    No other sources connected. 

    One correction to my earlier post: I read the low current value wrong, it is 20uA (not 2uA)

    Here are some new data with a power supply acting as a solar panel

    When solar panel voltage is falling
    VIN2 Voltage BAT Current ACFET2-RBFET2 Charging
    3.6V -9mA ON YES
    3.5V 470uA ON NO
    3.4V 470uA ON NO
    3.3V 470uA ON NO
    3.2V 470uA OFF NO
    3.1V 470uA OFF NO
    ...
    2.5V 470uA OFF NO
    2.4V 20uA OFF NO

    When solar panel voltage is rising:
    VIN2 Voltage BAT Current ACFET2-RBFET2 Charging
    2.5V 20uA OFF NO
    2.6V 20uA OFF NO
    2.7V 470uA OFF NO
    ...
    3.4V 980uA ON NO
    3.5V 980uA ON NO
    3.6V -9mA ON YES

    kind regards,

    Andreas

  • 0 in reply to Andreas Sjöblom
    TI__Prodigy 330 points

    Hi Andreas,

    Thank you for the new information. I have a couple of additional questions.

    1) Try removing the JP30 shunt to disable the EVMs pull-up LDO. Does this reduce the Iq to within the range in the datasheet?   

    2) Can you confirm that the ADC is disabled during the excessive current consumption?

    Best Regards,

    Austin

  • 0 in reply to Austin Allen
    Prodigy 10 points

    Hi Austin,

    Sorry for the late answer.

    Thanks for the questions, here are the answers:

    1) JP30 was already removed during the measurements. With JP30 connected, BAT-current will increase by 2mA

    2) I can confirm, by reading bit 7 in reg 0x2E as 0, that ADC is disabled. (As I have all registers as default and default for bit 7 in reg 0x2E is 0) By enabling ADC the BAT-current will increase to 980uA until the VIN2 Voltage goes above 3.6V and the charging starts  

    kind regards,

    Andreas

  • 0 in reply to Andreas Sjöblom
    TI__Prodigy 330 points

    Hi Andreas,

    What is your VSYSMIN set to? It sounds like your battery may be in supplement mode to regulate VSYS. If it isn't already, try setting your VSYSMIN to the minimum of 2.5V. 

    Regards,

    Austin

  • 0 in reply to Austin Allen
    Prodigy 10 points

    Hi Austin,

    The issue remains unchanged, with VSYSMIN set to 2.5V, I had it set to 3.5V (default value)

    kind regards,

    Andreas

  • 0 in reply to Andreas Sjöblom
    TI__Guru**** 166596 points

    Hi Andreas,

    Unfortunately, this converter (and the pin 2 pin BQ25798 from which it was derived) pulls some current from battery when there is a boosting configuration (VBUS < VBAT).  There is no way to disable this.  Also, the input voltage is near or below the ICs UVLO so we have not characterized operation in this region.

    I recommend adding an input switch that disconnects the panel from the charger when its voltage is below 3.6V. The switch could be as simple as a PMOS FET with large sized resistor divider from source to gate.

    Regards,
    Jeff