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BQ24196: Vsys power cann't stable, STAT pin LED flicking without battary

user397859
Prodigy 140 points
Part Number: BQ24196

I have BQ24196 with my design,  to charge 1 cell battary and source system power, schematic as below , stand alone solution

issue is Vsys cann't out stable when DC_IN with 5V voltage, have tryed 12V, still cann't output stable

1. have checked SW pin, the PWM signal is not continue output, just like  pulse-pulse-pulse-no signal-pulse-pulse-no signal

2. Ilimit pin voltage measured with multimeter, 0.55---0.8V

3. have change R220 to 220 OHM, Vsys still cann't output stable

Pls help to provide suggestion for this issue. 

  • 0
    TI__Intellectual 1470 points
    Hi User,

    You mentioned that this was occurring without a battery attached. When this is the case you will see a cycle where the charger will charge the capacitors to the charge voltage, then they will discharge to below the recharge threshold, then the charger will charge them up again, and so on.

    The STAT pin LED shows when the charger is charging. It is flickering because the cycle will occur several times a second. Also, the switch node will be a square wave during the charging periods.

    It sounds like this is what you may be seeing. Can you clarify what you mean by the VSYS power not being stable?

    Thanks,
    John
  • 0 in reply to John Dorosa
    Prodigy 140 points
    Hi John,
    thanks for your reply.
    YES, just as you clarified. So, do you mean, battary must be attached if I need BQ24196 to provide the system power with Vsys ?
    What I mean is BQ24196 could not output Vsys normally without battary attached, Vsys could not above 3.7V(just 0.8V as measured)
  • 0 in reply to user397859
    TI__Intellectual 1470 points
    Hi Scott,

    The bus voltage should still be able to provide power to VSYS even without the battery attached.

    Your VSYS should be at the programmed max battery voltage (REG04). As a default this is 4.208V. Can you see what is written to that register?

    Thanks,
    John
  • 0 in reply to John Dorosa
    Prodigy 140 points
    Hi John,
    Cause we didn't connect I2C to BQ24196, so I cann't confirm the register value. And till now the device couldn't power system with Vsys, the system will reboot again and again, till we attached the battery, system will stable.
    So we will connect I2C to BQ24196 at next design.

    thanks!
    Scott