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BQ77915: CHG not turning on when load is connected after OV.

Varun Reddy1
Prodigy 130 points
Part Number: BQ77915

Hello

The BMS is working fine when charging and  CHG turns off at full voltage. Later when I connect the load the CHG  pin voltage still remains at 0.3V on all the 4 ICs.

Kindly let me know the reason for this.

  • 0
    TI__Guru 54715 points

    Hi Varun,

    When cells are charged to OV, the part goes to OV mode.  Recovery from OV is by hysteresis as summarized in the BQ77915 data sheet table 1.  If sufficient current is drawn from the battery to activate the body diode protection threshold, the CHG FET will turn on to avoid heating.  See the data sheet section 9.3.10 and section 10.1.1.7. 

    It is common for a system to charge the cells to a voltage below the protection level.  So a system may charge to 4100 mV while the OV threshold is selected at 4200 mV.