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BQ24715: BQ24715 DPM

Jeff Yang76
Intellectual 490 points
Part Number: BQ24715
Other Parts Discussed in Thread: BQ25700,

Hi,

BQ24715  IDPM function is different with BQ25700 DPM function, right?

If using 12V/1.5A adapter, set BQ25700 input current limit to > 1.5A, if input current above 1.5A, BQ25700 can adjust charging current keep input voltage above VDPM,

But If using 12V/1.5A adapter, set BQ25715 input current limit to > 1.5A, if input current above 1.5A, BQ25715 seems force stop charging, is it normal?

Thanks!

Jeff

  • 0
    TI__Genius 10385 points

    Jeff,

    If you disable IDPM by setting IDPM_EN to 0, does charging stop with the same adapter? Please send me the value for the charge options register before and after you connect the adapter.

    Thanks,

    Ricardo

  • 0 in reply to Ricardo
    Intellectual 490 points

    Hi Ricardo,

    I used same adapter for both EVM. This figure is BQ24715 register setting. thanks!

  • 0 in reply to Jeff Yang76
    TI__Genius 10385 points

    Jeff,

    I am assuming this register snapshot is before the adaptor is connected as the device is in low power mode (battery-only). Could you also provide the register bits after you have connected the adaptor? I would like to see if any of the bits change.

    Thanks,

    Ricardo

  • 0 in reply to Ricardo
    Intellectual 490 points

    Hi Ricardo,

    Please refer to below register setting when first connect adapter. After connect adapter, I follow EVM guide set 0x12 to 8156, 0x15 to 8400mV, 0x14 to 2048mA.

  • 0 in reply to Jeff Yang76
    TI__Genius 10385 points

    Jeff,

    This is very unusual. Even after the adaptor is connected you seem to remain in low power mode. Does the device begin charging if you set REG0x12[15] to 0?

    Thanks,

    Ricardo

  • 0 in reply to Jeff Yang76
    TI__Genius 11850 points

    Hi Jeff,

    Yes, the behavior you're seeing is expected. I confirmed this on a BQ24715 EVM.

    The BQ24715 only has IINDPM, not VINDPM. Since there is no VINDPM, the BQ24715 cannot reduce the charge current in order to maintain the adapter voltage above a specified level. Therefore, if you exceed the adapter's current limit, then the adapter voltage will crash.

    The waveform below demonstrates this. I used a 20 V adapter with a 0.5 A current limit. When I increase the charge current too high, then the adapter's 0.5 A current limit is exceeded, and VBUS begins to crash. When ACDET falls below 2.4 V, the BQ24715 thinks the adapter has been unplugged, and the device stops charging.

    Here is another waveform showing the same test, but with a 24 V adapter. You can clearly see that charging stops when ACDET falls below 2.4 V.

    In order to stop the adapter from crashing, the correct way to configure the BQ24715 is to set the InputCurrent() register to a value lower than the adapter's actual current limit. That way, if IINDPM is enabled (ChargeOption() bit [1]), then the BQ24715 will limit the charge current so that the adapter's current limit is not exceeded.

    For example, in the waveform below, I set the InputCurrent() register to 384 mA. Even as I continued to increase the ChargeCurrent() register setting, the input current was clamped, so the adapter never crashes and causes charging to stop.

    Best regards,

    Angelo

  • 0 in reply to Angelo Zhang87
    Intellectual 490 points

    Hi,

    Got it, we may choose other charger IC with VINDPM function  to solve this issue.

    Thanks!

    Jeff