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BQ24780S: BQ24781: PROCHOT behavior regarding ACOK and IDCHG

Antony Lin
Genius 13480 points
Part Number: BQ24780S
Other Parts Discussed in Thread: BQ24781

Hi,

Customer is checking PROCHOT behavior with scenario described below.

  1. NB system runs under a heavy system load with charger adapter connected
  2. Remove the adapter from the NB and expect to see PROCHOT triggered from ACOK and IDCHG events.

Related set-up and result is described as below.

  • Register setting as below.  IDCHG threshold is 8192mA

  • Resistor value between SRP and SRN is 10mohm
  • The waveform at the moment when adapter is removed as below. 
    • CH1  BQ24781/PROCHOT
    • CH2: Battery discharge current
    • CH3: BQ24781/ACOK

This PROCHOT is based on ACOK instead of IDCHG based on a separate test previously with IDCHG or ACOK disabled in 0x3DH.  From the above test result, the questions are,

  1. Why we didn't see a PROCHOT triggered from IDCHG event.  Based on the IDCHG threshold configured as 8192mA and deglitch time as 100uS, do you have any comment why PROCHOT is not triggered for IDCHG event?
  2. From ACOK falling edge to PROCHOT driven low it takes 105.6ms.  Is it a reasonable delay?  I can't find related spec in the datasheet.

Thanks!

Antony

  • 0
    TI__Expert 5330 points

    Hi Anthony,

    I am measuring nearly instantaneous transition of /PROCHOT with /ACOK on the EVM and I am seeing 100 uS deglitch with IDCHG /PROCHOT. 

    Is there any chance that EC is coming in at 100 mSec and making  change to the configuration?  With LPM enabled, /PROCHOT does not work, so if EC came in after 100 mSec and disabled LPM, then you would see a delay like the scope captures you show.

    It seems that the IDCHG dies down after 50 mSec, so if you are never getting an IDCHG /PROCHOT and you are only getting the ACOK 100 mSec after you should, it seems like something in the system is keeping /PROCHOT disabled for 100 mSec after adapter removed.  Again, LPM setting could do this, or if the EC is going in and making configuration changes, that could be what is doing it.  But I don't see anything like this 100 mSec delay on the EVM.

    Regards,

    Steve

  • 0 in reply to Steve Preissig
    TI__Expert 5330 points

    Hi Anthony,

    I haven't seen a response on this in about two weeks, so I am assuming that you were able to resolve the issue and I a going to close the thread.

    Thanks,

    Steve