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BQ78350-R1A: Charge FET toggling

Jeffrey Wright
Expert 2875 points
Part Number: BQ78350-R1A
Other Parts Discussed in Thread: BQ76920, BQ78350-R1

Hello;

All the sudden, the charge FET keeps cycling ON - OFF - ON - OFF. On for ~3 seconds...then OFF for ~5 seconds....repeatedly.  It's doing it at all charge or discharge current levels, including 0A.  The 920 is not flagging any Alerts. It's only the charge fet - the discharge fet is acting normal. I've not changed the Fuel Gauge parameters such as CHG_CURRENT_THRESHOLD, which is sitting at its default value. So I expect it to open the charge fet at end-of-charge, but not during charge. I've obviously introduced some error into the parameters, but have yet to find it.

Does anything come to mind as to a possible cause????

Thanks!

  • 0
    TI__Guru* 81034 points

    Hi Jeff,

    You mentioned in your email message that this starting occurring after you enabled PFs on the BQ78350-R1. If the BQ76920 is not flagging any Alerts, it is most certainly a software based protection (not a hardware protection from the BQ76920). I would focus on the BQ78350-R1 PF and Safety status registers to understand which protections are taking effect. It is always good to read these status registers along with other parameters (cell voltages, currents, soc, etc) to understand exactly what is being triggered and why.

    Best regards,

    Matt