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BQ24072 LED status

Jones Yu
Prodigy 130 points
Other Parts Discussed in Thread: BQ24072, BQ24072EVM

Hello,

We encountered issue on the LED status of the BQ24072, when it is used as a standalone charger.

When quickly removing and re-connecting the battery pack from and to the BQ24072, the charging LED does not indicate correct charging status although the battery pack is being charged.

Same problem is found in the BQ24072EVM.

Would you please advise?

Thanks.

  • 0
    TI__Mastermind 20570 points
    Can you provide scope capture on this issue (VBAT,/CHG, VIN).

    What is the battery voltage?
    What is the "correct charging status" you are referring to? Can you be more specific on the status on the /CHG before and after you reconnecting the battery pack?
  • 0 in reply to Jing Zou
    Prodigy 130 points

    Battery Voltage: 3.396V

    Testing procedure

    1) Plug in DC5V to provide power to VIN

    Channel 1 – VIN

    Channel 2 – \CHG

    2) Plug in battery for charging on cradle. (This capture shows the correct behaviour) \CHG signal go low to light the LED.

    Channel 1 – VIN

    Channel 2 – \CHG

    3) Remove the battery and plug the battery again quickly. Sometimes, the \CHG signal will not go low enough to light the LED connecting to it. At the beginning, \CHG is 4.08V and it is only 3.6V when battery plugged in, while VIN signal doesn't change.

    Channel 1 – VIN

    Channel 2 – \CHG

    4) The battery is charging, but the \CHG signal is not correct. Hence, the connected to this pin not lighting up.

    Channel 1 – VBAT

    Channel 2 – \CHG

    Thank you.

  • 0 in reply to Jones Yu
    TI__Mastermind 20570 points
    Can you share your schematic? Is the /CHG pulled to OUT or BAT? What is the value of the pull up resistance?
  • 0 in reply to Jing Zou
    Prodigy 130 points

    Please refer to below schematics. Thanks.

  • 0 in reply to Jones Yu
    TI__Mastermind 20570 points
    The /CHG is low only in the first charge cycle. Once the battery is removed, VBAT goes to VBAT(REG) and charge current is 0. Then Battery detection routine starts. VBAT is regulating at VBAT(REG) and pull down every 250ms.

    If you remove the battery and wait for a full battery detection cycle to run, then the IC starts a new charge cycle. /CHG goes low again.

    If you re-attach the battery before a full cycle of battery detection routine is run, then the IC thinks termination condition is met during battery removal and recharge condition is met when re-attached the battery which voltage is lower than VRCH. /CHG stays high Z.