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BQ25895: ADC charge current wrong value for high fast charge current, with limited input current source

TISL
Expert 4620 points
Part Number: BQ25895

Dear Support,

My customer uses our EVM, with Vbus connected to a 5V source limited at 80mA for his tests (to simulate a solar panel).

When programming the charge current at 320mA, our ADC reads a charge current of 100mA; which is coherent and which has also been measured physically (90mA) between our charger and the battery.

Bellow are these settings which works well:

But when the charge current is set to 1.536A, the ADC current reads 0, while 90mA are still measured between the charger and the battery:

Are there any explanation and workaround on this behavior?

Regards,

  • 0
    TI__Guru** 105590 points

    Hello,

    The resolution for this bit is not very higher (50mA steps) This may be part of the issue. Will the ADC always read 0mA after multiple reads?

    Also the following conditions must be met to read the ADC, if you are in VINDPM the bus voltage may be too low and you're changing modes: V(VBUS) > VBAT + V(SLEEP) and VBAT > VBAT(SHORT)

    Sincerely,

    Wyatt Keller

  • 0 in reply to Wyatt Keller
    TI__Expert 4620 points

    Hi Wyatt,

    Yes we read 0mA each time, while 90mA is measured to the battery.

    As you can see in the print screen, Vbus is at 5V, Vbatt at 3.664V, so we have enough room of delta Vin/Vout.

    The weird thing is that the only change between the two tests is the charge current...

    Regards,

  • 0 in reply to TISL
    TI__Guru** 105590 points

    Hello,

    I will try to confirm in the lab tomorrow if I see the same issue on the bench. The setting of charge current should not influence the ADC value, especially since you're in VINDPM for both cases.

    Sincerely,

    Wyatt Keller

  • 0 in reply to Wyatt Keller
    TI__Guru** 105590 points

    Hello,

    I am able to see the same behavior as you, the only thing changed is the charge current register and that causes the charge current to become 0mA when there's around 100mA or below. I see that it works correctly at 150mA, but anything below will be reported as 0mA.

    We can discuss offline.

    Sincerely,

    Wyatt Keller