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BQ2973: Issue recovering from fault mode

Dave Kearney
Prodigy 85 points
Part Number: BQ2973

Tool/software:

Hi, I'm seeing some strange behaviour with the BQ29737 circuit. I'm using it with a single cell battery, no pack, connected directly to a charger as below(charger connected between Vbatt and GND). To test it I have been pulling the battery + and - rails above 4.3V and below 2.8V to confirm the OVP and UVP functionality, and while it kicks in and the FETs turn off at these expected set points, when I set the voltage back to within the normal region (say 3.5 - 4V) it doesn't recover. Interestingly, it only recovers when I either (a) short the cell- net to the system ground net (in the bottom right below) or (b) turn the charger on, then even after toggling the charger back off, the BQ has resolved it's fault. Any ideas? Does the circuit below look reasonable?

Many Thanks,

Dave

  • 0
    TI__Expert 4320 points

    Hi Dave,

    I am noticing a connection bypassing the MOSFETs. Can you show me that section of the schematic as well?

    Best regards,

    Thomas Rainey

  • 0 in reply to Thomas Rainey
    Prodigy 85 points

    Thanks for the reply Thomas, it's just a fuse which is not loaded, as a backup in case the BQ doesn't work correctly so will not be having any impact. Assuming the fuse isn't loaded, does the circuit look OK? It looks OK to me compared to the datasheet/evm schematic but it seems like there's something weird happening with the ground references.. Thanks, Dave

  • 0 in reply to Dave Kearney
    TI__Expert 4320 points

    Hi Dave,

    Your schematic looks good. I think the issue may be with your test procedure. I would just make sure you meet the recovery requirements listed in 9.4.2 Overcharge Status and 9.4.3 Over-Discharge Status. 

    Best regards,

    Thomas Rainey