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BQ24800: About ACDET deglith time

Norimichi Hosogai
Prodigy 230 points
Part Number: BQ24800

We would like to keep ACDET High recongnization(ACFET/RBFET on) when the transition period to Hybrid boost mode around 100us as below.
Because heavy load is started, AC adapter's voltage will be down until start Hybrid mode, then it has possivility that ACDET voltage is lower than threshold.

(1) Can ACDET's ignore AC judge until go to Hybrid mode ?

(2) If ACDET port has the deglitch time by hard ware etc., please teach this time for just to make sure. (10ms/ 1ms / 1us / 1ns…) 

(3). If ACDET port has not the deglitch time even though 1ns etc., when ACDET port level is High to low, if ACDET port level will be return to High immediatry, ACFET/RBFET will be not turn off? If is this correct,
please teach ACDET must be return High from Low within how many seconds for keep ACFET/RBFET still on?

Best regards,

  • 0
    TI__Mastermind 30825 points

    1. The BQ24800 can not ignore ACDET.

    2. The ACDET port deglitch time is set by register 0x37 [12].

    3. Yes, if ACDET port is low, ACFET/RBFEET turn off immediately. If ACDET goes high again, ACFET/RBFET will wait for the deglitch time to turn back on.

    There's a few features that the charger has to work for this situation though. You can program ACDET with resistors to detect a lower voltage. This means ACOK will never turn off when the adapter current dips. You can program the Input current limit, Reg 0x3F, to prevent from drawing to much current. You can also program peak power mode enable allow the charger to exceed the input current limit for 1,2,5, or 10 ms.

    You can also use a micro controller to pull up the ACDET port voltage so ACDET is always enabled.

  • 0 in reply to Ethan Galloway
    Prodigy 230 points

    Thank you for you reply

    >3. Yes, if ACDET port is low, ACFET/RBFEET turn off immediately. 

    When ACDET port High to Low, If ACDET port low time even if 1ns, ACDET/RBFET turn off immediatery? I would like to it as soonn as possible.

    We can't reduce the input currect limit for system performance now.

    Best reagrds,

  • 0 in reply to Norimichi Hosogai
    TI__Mastermind 30825 points

    Norimichi,

    The ACDET falling deglitch time to turn off the ACFET is 3 us.



    Regards,
    Ethan Galloway

  • 0 in reply to Ethan Galloway
    Prodigy 230 points

    Thank you very much.

    When ACDET port High to Low to High, and Low time is within 3us, ACDET is not judge low, and it mean that ACFET will turn OFF, is it correct? I'm sorry, if yuo can, please reply as soon as possible. 

    best regards, 

  • +1 in reply to Norimichi Hosogai
    TI__Mastermind 30825 points

    Norimichi,

    Yes, if ACDET is at a high signal and it goes low to high within 3 us, ACDET will not detect a low signal. In this situation, ACOK will stay on.

    Please keep in mind that 3 us is the average falling deglitch time for ACDET. We do not spec the upper and lower bounds of the falling deglitch time for ACDET.

    Ethan Galloway