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BQ24179: can we disable the Vbus automatically measure and update VINDPM?

Nan Zhang
Intellectual 1895 points
Part Number: BQ24179


Hi team,

      According to datasheet, the bq24179 would measure the VBUS and set the VIDPM as VBUS-0.7V(Vbus<7V). The customer use typeC as power supplying and data transferring. when they connect the their computer usb port at 5V, because of the poor power ability , the voltage of port on PC goes to 4.1V which would influence transferring the data. Could you please tell me how to disable the Vbus measurement?

YOURS

NAN

  • 0
    TI__Guru**** 168866 points

    Hi NAN,

    Unfortunately, there is no way to prevent this ADC read of the VBUS pin.  However, I do not understand the issue here.  The host can rewrite the VINDPM value after power up if needed.

    Is the issue the poor source test?  Poor source is independent of VINDPM measure and set.

    Regards,

    Jeff

  • 0 in reply to Jeff F
    TI__Intellectual 1895 points

    Hi jeff,

         Could you please tell me more detail about the poor source is independent.

    Jeff F said:
    Poor source is independent of VINDPM measure and set.

         Here is how they use.

    YOURS

    NAN

  • 0 in reply to Nan Zhang
    TI__Guru**** 168866 points

    Hi Nan,  

    The POR sequence when the charger powered from VAC is described as below: (with input power mux)

     After the charger wakes up, the adapter present comparator is activated, to monitor the VAC voltage.

     1ms after VAC1 (or VAC2) becomes higher than VAC_PRESENT, the output of the VAC present comparator becomes high, and the charger brings up the internal 1.8V bias to power the analog circuit.

     Another 2ms later, ACDRV1 turns on ACFET1-RBFET1 (or ACDRV2 turns on ACFET2-REBEF2).

     VBUS and PMID become high, VBUS_PRESENT signal becomes high.

     The input current sensing FET, QS, is turned on 100us after the VBUS_PRESNET signal becomes high.

     Around 150ms after VBUS becomes high, the REGN is turn on.

     Right after the REGN is turned on, the charger starts the poor source detection. It takes around 30ms for the charger to finish the poor source detection, once a good source is detected, the charger will pull low the /PG pin and set the PG_STAT register bit to 1.

     After a good input source is detected, the ADC reads the ILIM_HIZ pin voltage and VBUS voltage, and the charger will update the IINDPM register and VINDPM register based on those voltages reading.

    Poor source works as below:

    After REGN LDO powers up, the device checks the current capability of the input source. The input source has to meet the following requirements in order to start the buck-boost converter. 1. VBUS voltage below VVBUS_OVP 2. VBUS voltage above VPOORSRC (typical 3.4V) when pulling IPOORSRC (typical 30mA) Once the conditions are met, the power good status register bit, PG_STAT is set high and the /INT pin is pulsed to alert the host, the /PG pin goes LOW. If VBUS_OVP is detected (condition 1 above), the device automatically retries detection once the over-voltage fault goes away. If a poor source is detected (when pulling IPOORSRC, the VBUS voltage drops below VPOORSRC), the device repeats poor source qualification routine every 2 seconds. After 7 consecutive failures, the device sets EN_HIZ bit and goes to HIZ mode. Adapter re-plugin or EN_HIZ bit toggle is required to restart device operation.

    Regards,

    Jeff