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BQ25792: VAC1/2 switch question

Roy Chou1
Genius 14445 points
Part Number: BQ25792
Other Parts Discussed in Thread: TPS25751,

Tool/software:

Hi Team,

Our circuit is showing as below. VAC1 is 12V adapter and VAC2 is 5V from typeC. (TPS25751) 

First, the VAC2 presented and the charge current to battery was 700mA. (we set 700mA)

And then we plugged in VAC1(12V) and we used EN_ACDRV to switch the Vin from VAC2 to VAC1 and the charge current was also 700mA. At this moment, VAC1 and VAC2 were having voltage input. 

1. Then, we disconnected the VAC1(12V) and we found the BQ25792 will not auto-switch to use VAC2, is it normal?

2. We can use EN_ACDRV to switch the power input from VAC1 to VAC2, but we found that the charge current became 300mA~400mA. Do you have any idea? 

- We can replug in the typeC to let charge current recover to 700mA.

Regards,

Roy 

  • 0
    TI__Guru**** 154066 points

    Hi Roy,

    Regarding 1, no.  I just tested on bench with 2 power supplies.  Are you certain that the 5V USB-C output is available at the time of 12V removal?

    Regarding 2, what do the STATUS and FAULT registers report  at the switch over?  One of the DPM loops is likely limiting current.  

    Regards,

    Jeff

  • 0 in reply to Jeff F
    TI__Genius 14445 points

    Hi Jeff,

    Regarding to 1, I will check it.

    Regarding to 2, we found if we issued the 0x13 = 0x21(ACDRV1/2 disable). The issue can be fixed. And we read the 0x13 after issuing the command I said, the 0x13 is 0xA1.

    So I agree that the BQ part may limit the current from ACDRV2. But do you think above result is ok or not?


    Regards,

    Roy

  • 0 in reply to Roy Chou1
    TI__Guru**** 154066 points

    HI Roy,

    Disabling both ACDRVx resets the ACDRV logic. If one of channels fails poor source detect, it gets locked out and requires a reset.  I suspect that is the issue.

    Regards,

    Jeff