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BQ40Z50-R1: Timing specification for OCP and AOLD

Matthew Stevens
Prodigy 10 points
Part Number: BQ40Z50-R1

Hi.

I've configured an Overcurrent Protection and Overload Protection on a bq40z50-R1 but they both fail to trip within the datasheet specification.

For example, the overload in discharge is set to -13.86mV threshold with a delay of 31ms [AOLD:Threshold] = 0xF2 with [AFE:Pretection Control:RSNS] = 0; however, out of three tests we get a trip time of 61.5ms, 96.5ms and 105.4ms. These are well outside the +/-10% specified in the datasheet.

For completeness: [AOLD:Latch Limit] = 0. [AOLD:Counter Dec Delay] = 0. [AOLD:Recovery] = 0. [AOLD:Reset] = 0

I’ve been combing the datasheet and TRM with no avail; any help would be appreciated.

Regards,

Matt

  • 0
    TI__Guru** 105770 points

    Hello Matt,

    Can you share your .gg configuration file and any scope captures you have of the protections being triggered?

    Sincerely,

    Wyatt Keller

  • 0 in reply to Wyatt Keller
    Prodigy 10 points

    Hi Wyatt, 

    Thank you for getting back to me. The attached plot is of the AOLD protection. 

     

    bq40z50_r16.4(Unreleased).gg.csv

    Regards,

    Matt. 

  • 0 in reply to Matthew Stevens
    TI__Guru** 105770 points

    Hello Matt,

    Can you explain the graph further? Are each of the lines the discharge current for a different test?

    The gauge also has some detection delay specified in the datasheet, which can be up to 30ms: 7.32 Timing Requirements: OCD, SCC, SCD1, SCD2 Current Protection Timing

    Are all those tests with the same discharge current? It looks like you're seeing 40ms variation with the same test from the graph. 

    Sincerely,

    Wyatt Keller

  • 0 in reply to Wyatt Keller
    Prodigy 10 points

    Hi Wyatt.

    Yes, each of the lines is a repeat of the same discharge test with the same 15.1A discharge current and 13.86A threshold. 

    The timing requirements you are referring to in section 7.32 is the programmable range, as per section 2.7 (and appendix A) of the technical reference manual. I have set [AOLD:Threshold] to 0xF2, which represents 31ms delay and -13.86mV threshold. The tolerance I am expecting is (tacc) in section 7.32 which is +/-10%. 

    You're right, there is about a 45ms variance between the three tests; this is no where near the +/-10% specified and the quickest trip delay is at least double the 31ms programmed. 

    Regards,

    Matt. 

  • 0 in reply to Matthew Stevens
    TI__Guru** 105770 points

    Hello Matt,

    If you test with higher discharge rate will the protection trigger when expected? Sometimes the protections are slower or inconsistent around the current the y are set at.

    I will also check internally.

    Sincerely,

    Wyatt Keller