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BQ25703A: IIN not being read

Laurence Symonds
Intellectual 545 points
Part Number: BQ25703A

Hi

I am having issues reading any values from the IIN register on the BQ25703A.

I have tried both continuous and one shot modes and no luck. The other registers are reading in fine, just the IIN reading is not coming through.

The custom PCB design is based on the schematic from TIDA-01515. I can manually sense a voltage difference between the SRN and SRP pin but I never see anything on the register.

Are there any registers that may disable IIN?

Thanks

  • 0
    TI__Mastermind 25800 points

    Hey Laurence,

    When you say are not able to read it, first which register address are you trying to read from? 

    Does the I2C transaction not ACK? Or you always read a value of 0mA?

    Regards,

    Joel H

  • 0 in reply to Joel Hernandez II
    Intellectual 545 points

    Hi Joel

    Thanks for the reply.

    Sorry, I was a bit vague. I am getting an ACK, I'm just reading a value of 0mA always.

    To set up, I write a 0 to EN_LWPWR and WDTMR_ADJ in chargeOption0

    write 1 to ADC_CONV, write a 1 to EN_ADC_IIN and any other bit in ADCOption (0x3A)

    Then when I read the values from the ADC register, all of the registers are returning values as expected apart from IIN.

    It always returns a 0.

    I can read a value on PSYS but only when the power is being drawn from the battery. When the adapter is plugged in and it is charging the battery, or just running the system from VBUS, there is no value in the PSYS register. It also returns 0. I guess this is because the PSYS calculation is done using the IIN register.

    Thanks

  • 0 in reply to Laurence Symonds
    TI__Mastermind 25800 points

    Hey Laurence,

    Can you measure the differential voltage across the RAC resistor to determine how much current is passing through it?

    And I looked back at your original post where you mention SRN and SRP but also IIN. The differential voltage across SRx monitors the battery current, IBAT; not the input current, IIN. Do you have an input present? Or are you trying to read the battery current?

    Regards,

    Joel H

  • 0 in reply to Joel Hernandez II
    Intellectual 545 points

    Hi Joel

    Thanks for the reply.

    Sorry, I made a mistake there. I meant ACN and ACP.

    Directly across the 10mOhm RAC, I'm measuring 1.7mOhm, which tallys up with the 1.65A at 20V I'm reading coming through the USB-C line.

    Thanks

  • 0 in reply to Laurence Symonds
    TI__Mastermind 25800 points

    Hey Laurence,

    A few more questions: 

    How are you reading the register? And how fast are you sampling the register? Are you in the 1-shot pulse more or the continuous 1-sec ADC read?

    Regards,

    Joel H

  • 0 in reply to Joel Hernandez II
    Intellectual 545 points

    Hi Joel

    thanks for the reply.

    I am in the continuous mode but am not actually reading continuously.

    I think continuous is preferable to save time on the I2C bus.

    Sampling happens manually at the moment, but it doesn't make a difference if I sample regularly at say once a second, it still reads 0.

    Thanks

  • 0 in reply to Laurence Symonds
    TI__Mastermind 25800 points

    Hey Laurence,

    I just tried this on my EVM.

    I have a 20V input, 14V battery voltage, with a 4S CELL_BATPRESZ condition so the maximum charging voltage defaults to 16.8V.

    I set the charge current to 2176mA, which gives me about 1.67A on the input. 

    I enabled the ADC 1-sec continuous mode, enabled the EN_ADC_IIN bit, and then started the ADC. 

    From there, I was reading 1600mA from the ADC.

    Can you confirm you test conditions? Like input voltage, battery voltage, load or charging current, and CELL_BATPRESZ pin setting?

     


    Regards,

    Joel H