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BQ25172EVM: IF NiMH Battery does not connect, what's level of "STAT" pin ?

george Wu
Prodigy 20 points
Part Number: BQ25172EVM
Other Parts Discussed in Thread: BQ25172

Tool/software:

Hi team, we want to know how to distinguish if NiMH battery connect or not by pin STAT ?!

the resistor setting are Vset = 18K Ohm(3-cell + intermittent charge), Iset = 6.8K Ohm(45mA), TMR = 3.6K Ohm(22hr)

Vin = 5 ~ 12V, pin STAT rework to pull high 27K Ohm to 3.3V only,

and then we got the different waveform of pin STAT, it seems that the STAT waveform depend on Vin level !

this phenomenon is unexpect for me !!

please help to tell us what wrong ?

thank you.

  • 0
    TI__Guru* 76046 points

    Hi George

    This behavior is expected for a no battery conditions.  Unit will charge the output capacitor to OVP point, 1.7V / cell then shut off.  Output capacitor voltage will decrease to 1.33V / cell then restart charging and cycle repeats. Due to deglitch time for OVP and Recharge the voltage may not be exact.

    The BQ25172 is not designed with a battery detect feature.