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BQ40Z60EVM-578: AC Present input pin (ACP) stays hi when AC is removed (any work around?)

TK82
Intellectual 725 points
Part Number: BQ40Z60EVM-578
Other Parts Discussed in Thread: BQ40Z60, BQ40Z50-R2

Hi,

The AC Present input pin (ACP pin31) stays hi when AC is removed (any work around?).

Scenario:

The battery voltage is leaking back to the ACP pin and holding it up (thereby confusing the charger chip to think it should be charging).

The ACP pin should be driven lo when the AC power is removed but this is not happening.

The battery voltage is leaking back through Q8 body diode (hi side charge FET) and Q5 thereby holding the ACP hi (not good).

This is causing the charger chip (bq40z60) to try charging the battery from the battery (??) thereby drains the battery prematurely when our circuit is OFF.

thanks,

Tom

 

  • 0
    TI__Mastermind 42535 points
    Have you set NR bit in DA config? If yes, please reset it.
  • 0 in reply to Batt
    Intellectual 725 points
    Hi,
    We are using a Non Replaceable Battery with NR = 1 normaly and not monitoring SYSPRES input.
    Are you saying to set NR = 0 for normal operation?
    or
    are you saying to Reset (toggle the NR bit to 0 then back to 1 for normal operation) ?

    I will look further into the documentation for all the consequences if NR = 0 for normal operation.

    thanks,
    Tom
  • 0 in reply to TK82
    Intellectual 725 points

    hi,

    Is there any explanation how the ‘Vacp Hysteresis’ register setting is determined?

    I believe the “BATTERY ACP REMOVED Mode” is a misleading typo (ACP) that lead us down this path and was not the reason for our problems (NR= ??).

    The real problem was the ‘Vacp Hysteresis’ register was incorrectly set at 1500mV causing the ACFET signal (pin 29) to never shut off.

    Changing to the default ‘Vacp Hysteresis’ = 0mV solved the problem.

    see attached reference doc...

    thanks,

    Tom

    Vacp_Hysteresis.docx

  • 0 in reply to TK82
    TI__Mastermind 42535 points
    Hi Tom,

    I'm happy that you managed to resolve the problem. Sorry, you're right, the documentation is spotty and we're working on improving it. Thank you for using our product.
  • 0 in reply to Batt
    Intellectual 725 points

    i have not seen any recent changes to SLUUA04D March 2016 (bq40z60TRM) and suppose all developers have moved onto the more recommended bq40z50-R2..

    T