BQ25895: BQ25895 failure analysis

Will Wang47

Part Number: BQ25895

Hi team,

Customer is using our BQ25895, and they are meeting failure on some of there product, the Failure phenomenon are as below:

① When PCBA is not powered on, the DC impedance of Vbat pin and VSYS pin is only about 5Ω;
② When VBAT supplies 4V using Keithley, vsys voltage is about 3.26V, and vbat has 240mA current output.
③ The DC impedance of Vbat and GND is 194Ω;
④ When plugged into USB for charging, Vbat is set to 4V. At this time, the charger status indicator is always on, and the VSYS voltage is 4.23V. At this time, VBAT does not charge but outputs 65mA current.

The following is the schematic, could you give some comments on this?

Thanks and Best Regards,

Will

over 5 years ago

0 Joel Hernandez II over 5 years ago

TI__Mastermind 25800 points

Hey Will,

If the BQ25895 IC is removed from your board and the battery is attached, do you see any current pulled from the battery?

Regards,

Joel H

0 user6106807 over 5 years ago in reply to Joel Hernandez II

Prodigy 100 points

Dear,Joel

If remove bq25895 from the PCB，there is no current to the system from the battery。

and we test the resistance value between BQ25895 VBAT Pin and vsys pin which have been removed from the board，the value is very small, about 5 Ω。It seems the IC is broken.

0 user6106807 over 5 years ago in reply to Joel Hernandez II

Prodigy 100 points

Dear, Joel

There is no current pulled from the battery if you removed it from the board.

0 Joel Hernandez II over 5 years ago in reply to user6106807

TI__Mastermind 25800 points

Hello,

How many of your PCBs are failing?

Do they function normally and eventually fail, or are they DOA?

Regards,

Joel H

0 Will Wang47 over 5 years ago in reply to Joel Hernandez II

TI__Expert 7750 points

Hi Joel,

Thanks for supporting this case. Customer get the cause of this fail. Because they use keithley battery simulator connect to the charger VBAT. They find when they remove the simulator, a surge is observed, peak voltage is 9.7V, so this may cause the charger damage.

0 Joel Hernandez II over 5 years ago in reply to Will Wang47

TI__Mastermind 25800 points

Hey Will,

Yes, 9V will likely damage the device, especially at VBAT where the absolute max rating is 7V.

In our internal testing, we also the Keithley Battery Simulator, but also add a large 100,000uF capacitor to the direct output of the charger to avoid surges like this.

You may also consider a TVS diode or Zener clamp to help mitigate this effect for your development.

Feel free to post a new thread if any further issues are encountered.

Regards,

Joel H

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BQ25895: BQ25895 failure analysis