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bq24773 want to remove BATDRV fet

Ed Walker
Prodigy 5 points
Other Parts Discussed in Thread: BQ27220, BQ24773

I want to use a bq27220 gauge with the bq24773 charger.
And I want to use the bq24773 current sense resistor as the gauge sense resistor.

Since the BATFET would be in series with the battery it will affect the gauge.

What are the consequences of removing the BATFET, replacing it with a short to allow a direct connection to the battery?

  • 0
    TI__Guru 56650 points

    1. After remove BATFET, bq24773 cannot maintain the minimum system voltage when  the battery voltage is lower than the minimum system operation voltage.

    2. After remove BATFET, customer has to control the pre-charge current with their own circuit.

    3. After remove BATFET, bq24773 charging cannot be terminated after the battery is fully charged.

    4. At BATOVP or SYSOVP abnormal condition, customer should be able to turn off the charging path.

    I would recommend keeping BATFET. NVDC charger has been on the market for long time. What concern do you have between BATFET and the gauge?

  • 0 in reply to Wang5577
    Prodigy 5 points

    Thought was to use BQ27220 gauge, and use the bq24773 current sense resistor as the sense R for the gauge.
    But this would put the BATFET in series with the battery and cause some problems.

    That is why we needed to know the details of removing BATFET, which you explained very well.

    I believe I will try a BQ27621 voltage based gauge and place it after the BATFET right before the battery.

    Thank you for your thoughts.