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BQ24780S: Question regarding operation

Kevin Braun47
Intellectual 450 points
Part Number: BQ24780S
Other Parts Discussed in Thread: BQ24725A, BQ2002, BQ2000

Hello,

Is there enough headroom in the BQ24780S to charge 2 x NiMH cells (in series) at 800mAh with an input of 4.2V ?  If not, is there a better part to use?

Thanks,

...kevin

  • 0
    TI__Guru 56650 points

    Same as other SMBus chargers (bq24725A/35...), bq24780S can charge different type battery chemistries. But, it needs the host controller to control the charge current, charge voltage, charge termination, trickle charge and safety timer...

    4.2V input is too low for bq24780S. For example: the REGN is lower than VCC, it could be even lower than 4.2V. It could cause the BTST capacitor voltage too low: not higher enough to drive the switching FET; frequency refresh pulses.

    What is the input voltage is range? If the 4.2V input has a tight voltage range, please check bq2002 linear NiMH charger.

    If the maximum input voltage is much higher than 4.2V, please check the bq2000 NiMH switching charger.