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bq24157: bq24157 REG00[b5:b4]=11 but REG00[b2:b0]=000 when charging is enabled

Yang Qin2
Prodigy 100 points
Part Number: BQ24157

Dear charger team.

Customer found one of their smartphone prototype reports fault status with REG00[b5:b4]=11 but REG00[b2:b0]=000 when Vbus is attached. the below are all register log within the fault status: REG00-REG06

 0xb0    0xc0    0xb6    0x51    0x79    0x04    0x7c

the OTG pin is pulled up to VREF of bq24157 but OTG_EN=0.

we did some tests. if we plug a good adapter with charging enable, and then reduce Vbus voltage down to the range of 3.8V to 4V, we can see REG00[b5:b4]=11 but REG00[b2:b0]=000. but there is no DPM active status.

could you please help to check what kind of condition causes REG00[b5:b4]=11 but REG00[b2:b0]=000? what is status of bq24157 when a good adapter drop down to range UVLO<Vbus<Vin_min during the charger?

Thanks in advance.

best regards,

Yang

  • 0
    TI__Expert 8230 points
    Hello Yang,

    I tested this on the EVM and this behavior occurs when the VBUS drops between the bad adapter and sleep comparator thresholds. When this happens, the device will report a fault and set REG00[5:4] = 11. However, since the fault registers clear after each read, the host may read an I2C packet where REG00[2:0] = 000 and on the next packet it reads the fault, in this case, REG00[2:0] = 011.

    Depending on how fast the host is polling the fault register, it might miss the fault event. On the EVM, with a 1 second continous polling rate, I was able to capture the toggling between REG[2:0] = 000 and REG[2:0] = 011. Increasing the polling rate to less than 1 second, I started to miss the fault event. I suggest repeating the test on the customer's board and decreasing the I2C read rate and see if the correct fault condition is detected.

    Regarding the lack of DPM active status, when VBUS is at these voltage levels, the converter is disabled. During charge mode, DPM cannot be determined if there is no switching.
  • 0 in reply to Fernando Lopez
    TI__Prodigy 100 points
    Hi Fernando,

    Thanks for your reply. I was wondering what is the condition triggering bad adapter detection process? when VBUS PoR and charging enable or when Vbus drop down to bad adapter detection threshold? in customer's test, the first Vbus power on voltage is good, and then the Vbus voltage is dropping down the range of 3.8V to 4V. Do you mean the bad adapter detection process is implement?

    customer's polling rate is 5s.

    Thanks and best regards.
    Yang
  • 0 in reply to Yang Qin2
    TI__Expert 8230 points

    Hello Yang,

    Bad adapter detection is performed at POR. However, if the VBUS drops between the UVLO and VIN(min), the bad adapter detection will begin. It will fail since the VBUS is below VIN(min) and send a pulse on the FAULT pin and set REG00[2:0] = 11. After 2 seconds, it will repeat the adapter detection process. Monitoring the FAULT pin, I would expect a pulse every ~2secs under the test conditions.