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BQ25101H: /CHG output pin stays at '0' for batteries almost charged

TISL
Expert 3785 points
Part Number: BQ25101H
Other Parts Discussed in Thread: TPS62743

Dear e2e Community,

One of my customer has the following issue with our BQ25101H charger:

When they try to use a battery which is mostly charged (~ >4.1V), the /CHG pin stays at '0' (in charge mode) even if the charge is completed (Vbat>4.3V and output current measured at 0). It's finally going into a floating state after 1 or 2 hours. This behavior happens in both cases: with or without pic current coming from the system (TPS62743 + NCP170). Note that if the battery is removed during the issue, /CHG remains low.

If they use an empty battery, the /CHG signal works properly.

You will find below the schematic of their board. The CHG output is connected to a 40kohm pull-up.

Could you explain us this behavior?

Is there something where we could act to solve it?

Regards,

  • 0
    TI__Guru 65616 points
    As you indicated it sounds like bq25101H is not completing charge. The fast charge current set by R1 is 67mA with termination at 10% of that or 6.7mA.

    A couple of things to check:
    1.) Voltage on the battery, should be 4.35V.
    2.) Measure voltage at ISET with a scope with input current to system, compare input current with voltage at ISET.
    3.) Look for ripple or noise on the voltage at ISET near termination.
    4.) If a high ripple is present the Optional RC ckt, 2.7k and 10nF figure page 22 may help

    Note -- /CHG will be low during the first charge cycle only after that it will be float.