BQ24600: High Side MOSFET dies, when a short circuit is applied to the battery output!

Yannik Lorösch

Part Number: BQ24600
Other Parts Discussed in Thread: BQ77915,

Good day,

My company develops a battery board, for a product. We use a BQ77915 as our BMS and a BQ24600 as a charger.
The Battery is 5S1P LiIon with 2Ah per Cell.

The failure happens only in a few protection modes when the Battery Output is shorted to BAT- and when an OCD is detected while the charger is connected. The failure is that the High-Side MOSFET blows, but not the low-side MOSFET, and the IC worked also as expected after replacing the MOSFET. I tried it a few times, always the same behavior.
We have quite high currents in this system up to 22A.

The Battery gets charged with 1.5A from a 24V PSU.

So is there any form of protection that I can integrate into the circuit, I already have a fuse.
Or maybe you could recommend a different IC that handles this problem better.

Please see the attached schematics for reference.

Have a nice day
Yannik

SCH_Zündbox_V4_Slave_BAT_1-CELLS_2024-04-30.pdf

over 1 year ago

0 Christian Moyer over 1 year ago

TI__Mastermind 32461 points

Hello Yannik,

I'm going to review your schematic and provide an update after I gather more information.

Best Regards,

Christian.

0 Yannik Lorösch over 1 year ago in reply to Christian Moyer

Prodigy 10 points

Hello Christian,

Thank you very much.
By now I have some new information, it is related to the current through the MOSFET:
I noticed that when the adapter goes out first, with a lower current-rated one, for example, the MOSFET does not blow.
So I suspect that the BQ24600 is feeding so much current into the path that the High-Side MOSFET blows.

I hope that helps.
Yannik

0 Christian Moyer over 1 year ago in reply to Yannik Lorösch

TI__Mastermind 32461 points

Hello Yannik,

Can you check your PCB Layout, and make sure it follows the BQ24600 PCB layout guidelines.

Best Regards,

Christian.

0 Yannik Lorösch over 1 year ago in reply to Christian Moyer

Prodigy 10 points

Hello Christian,

Yes I checked all of them, and they were already implemented on the PCB
I realized a mistake on my end today, I had a 3.3uH Inductor placed instead of the required 6.8uH.
This improved the problem significantly, but the MOSFET still blows like 10% of tests (same tests as before).

Thanks for your help.
Yannik

0 Christian Moyer over 1 year ago in reply to Yannik Lorösch

TI__Mastermind 32461 points

Hello Yannik,

Can you measure the current and voltage going in to the MOSFET when this issue occurs?

Best Regards,

Christian.

+1 Yannik Lorösch over 1 year ago in reply to Christian Moyer

Prodigy 10 points

Good day,

we could resolve the issue, it was related to high transient currents in a capacitor bank on the board, we fixed it by actively limiting the current from the charger to the system, with an eFuse, and it works perfectly now. We did over 1000 short circuit events and all where handled well.

Thank you for your help
Yannik

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BQ24600: High Side MOSFET dies, when a short circuit is applied to the battery output!