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BQ24295: BQ24295 can not work with battery mode

Star Xu
Genius 9645 points
Part Number: BQ24295

Hi

BQ24295 will no output of VSYS after the USB power supply is disconnected.

At the moment when the battery is inserted, VSYS will be output, but after that VSYS will only have a voltage of 0V, and the voltage at the BAT pin is 4.1V.

Below is the schematic.

R22 is not soldered, the TS pin is pulled up to 3.3V.

Please help check it.

Thanks

Star

  • 0
    TI__Mastermind 23655 points

    Hi Star, 

    Based on the description given I have a few questions. 

    1)Can you provide a read of all registers after VSYS drops to 0V? Has the BATFET been forced off (this is checked in REG07 bit 5)? 

    2)You mention "At the moment the battery is inserted" as part of the test conditions. Is the VSYS = 0V behavior observed in test condition when battery is always connected then device transitions from charging battery to battery powering SYS when USB adapter at VBUS is removed? 

    Best Regards,

    Garrett

  • 0 in reply to Garrett Kreger
    TI__Genius 9645 points

    Hi Garret

    Thanks for your reply.

    1. The status of REG07 is as shown below.
    2. When the battery is always inserted and the USB power supply is plugged in, the system outputs VSYS normally. But if the adapter is unplugged, VSYS quickly drops to about 0.04V.

    Please help check it.

    Thanks

    Star 

  • 0 in reply to Star Xu
    TI__Mastermind 23655 points

    Hi Star, 

    Based off the REG07 status you shared BATFET is not being turned off. When the device is in battery only mode the BATFET is the only thing between BAT and SYS pins. Therefore, it seems the BQ24295 charger device is not the reason VSYS is dropping. Can you have the customer check if their battery protector is preventing the battery from discharging?

    An alternate strategy to confirm the issue is not related to the IC is to check if a power supply connected at BAT or a battery simulator, such as a sourcemeter, is able to output to SYS normally when USB power supply is not present at VBUS. 

    Best Regards,

    Garrett