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BQ77915: ö

Stefan Backman
Prodigy 20 points

  • 0
    TI__Expert 3880 points

    Hello Stefan,

    1. OVP can also trigger if the voltage goes over 4.2V for over a second. You can try measure the voltage at the pins of the device over the period of time or watch it over an oscilloscope to ensure that’s not the case. Also, is the discharge FET also turned off? If so, that would imply OCC.

    2. The body diode of the CHG FET allows current to still be pulled from the load even though the CHG FET is turned on. 

    Best Regards,

    Alexis H.

  • 0 in reply to Alexis_H
    Prodigy 20 points

    Hello again!
    1. The discharge FET is turned on. I've measured each cell and it triggers once a cell hits exactly 4.0V

    2.So there is no issues with the OV test? it is supposed to act that way? I find it weird that during other fault detections, both current and voltage drops close to zero but not in this case.

    Best,

    Stefan

  • 0 in reply to Stefan Backman
    TI__Expert 3880 points

    Hello Stefan,

    1. Is that also the case for the voltage at the pins of the device versus at the battery cell? You might also want to use your power supply instead of actual cells to test if there are any inaccuracies.
    2. With how you conducted the OV test, it is acting as it is supposed to as the OV test ensures that the battery cells are not overcharged. The body diode allows the battery to discharge/current to still flow. During other fault detections, e.g. OW, OCC, OCD, etc., unless certain conditions are met to remove the fault, both the CHG and DSG FETs can be turned off indefinitely, resulting in a current/voltage drop closer to zero. Table 9-5. Fault Condition, State, and Recovery Methods, of the BQ77915 Datasheet, can give you more information regarding that.

    Best Regards,

    Alexis H.