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BQ76952: BQ76952 autonomous recovery

Charles Zhang1
Expert 3390 points
Part Number: BQ76952

Hi Team,

My customer wants to configure BQ76952 as fully autonomous recovery mode as OCD1 happens, they set-

OCD1:Threshold = 2 (4mV)

OCD1:Delay = 4 (19.8ms)

OCD:Recovery Threshold= -100mA

Protections:Recovery:Time= 10s

Mfg Status Init[FET_EN] = 1

However, when OCD1 happens, BQ76952 would turn off DEFT after 60ms which is later than the expected delay.

Besides, it won't turn on DFET again(cannot recover autonomously) even though the charge current has been above 100mA for 10s.

Is there any setting we miss here?

Regards,

Charles 

  • 0
    TI__Mastermind 27321 points

    Hello Charles,

    Charles Zhang1 said:
    However, when OCD1 happens, BQ76952 would turn off DEFT after 60ms which is later than the expected delay.

    What is DSG FET Protections A set to? The DSG FET can take up to 250ms to turn OFF if this register is not set to 0xE4. Technically setting it to this value bypasses the firmware delay.

    Charles Zhang1 said:
    Besides, it won't turn on DFET again(cannot recover autonomously) even though the charge current has been above 100mA for 10s.

    Two things could be happening here. 

    1- I see the OCD:Recovery Threshold is set to a negative number. Can they please change it positive? Recovery happens with a charging current (positive current). It should work still with -100 mA, but this can  be confusing since at that point you are telling the FW to recover the state of the FETs with a -99 mA current or greater. Change it to 100 mA and see if it fixes the issue.

    2- OCDL latch counter could be incrementing and the device won't fully recover until the latch counter drops down to zero. See below 



    2.1- If OCD2 and OCD3 are not going to be used, you can disable the OCDL latch counter in Settings:Protection:Enabled Protections C:[OCDL]

    Regards,
    Jose Couso

  • 0 in reply to Jose Couso
    TI__Expert 3390 points

    Hi Jose,

    My customer has set the DSG FET Protections A to 0xE4, and also changed the recovery threshold from -100mA to 100mA, however, they find that the recovery threshold is actually 200mA(charge current), which is not aligned with the setting, what's the possible cause here? BTW, is it possible to set BQ76952 recover from OCD1 after a fixed period of time(like10s) regardless the recovery current threshold?

    Regards,

    Charles

  • +1 in reply to Charles Zhang1
    TI__Mastermind 27321 points

    Hello Charles,

    200mA is the default value for OCD: Recovery Threshold. Are they reading back to check if the settings have been changed accordingly? 

    What can also be causing issues here is the OCDL latch counter as I explained in previous reply.

    I suggest they read this FAQ to see how OCD1,2,3 work. Pay closer attention to the last paragraph (this could be happening). Are they using OCD2, OCD3, or SCD? I would disable protections not being used to avoid delays.

    Regards,
    Jose Couso