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BQ24078: Power dissipation equation

Ted Thomas1
Prodigy 135 points
Part Number: BQ24078
Other Parts Discussed in Thread: BQ24076, BQ24070

Equation on page 33 of data sheet is:

P = [V(IN) – V(OUT)] × I(OUT) + [V(OUT) – V(BAT)] × I(BAT)

I think it should be this:
P = [V(IN) – V(OUT)] × I(OUT) + [V(IN) – V(BAT)] × I(BAT)
Current to the battery comes from Vin not Vout.
  • 0
    TI__Guru 72206 points
    Hello
    I think this is correct, but double checking.
  • 0 in reply to Bill Johns
    TI__Guru 72206 points

    The bq24076 / 78 data sheet Power dissipation equation (9) on page 33 does not take into account battery current thru Q1 only current supplied to OUT pin.  This will equation will be updated.

    An accurate equation can be found in bq24070 / 71 data sheet, equation (10) page 24.  See below.