BQ76952: Problem as soon REG1 switched on

Nick

Part Number: BQ76952

Please see attached schematic. As soon REG1 is switch on and set to 5V, circuit start drawing > 50 mA. Normally the current should be 1.2mA.

I removed the IC from board and it showing ~ 110 ohm resistance between REG1 pin and VSS pin. I changed the IC and same problem repeated. I also removed the second IC from board and it also showing ~ 100 ohm

resistance between Reg1 and VSS pins

I am using BCX56-16 , NPN transistor. Transistor is not damaged. Please suggest What could be the wrong ?

Thanks

over 3 years ago

0 Caleb Perez over 3 years ago

TI__Genius 11315 points

Hey Nitin,

If this has happened between 2 ICs there is most likely an issue with your board. Your schematic looks okay, so I'd recommend checking for shorts across capacitors or between the REG1 pin and ground itself. Measure the resistance on a new part before you solder it to the board again and see if it changes after testing. Let me know the results.

Thanks,
Caleb

0 Nick over 3 years ago in reply to Caleb Perez

Intellectual 672 points

The problem is with Q29, Transistor BCX56-16 by Nexperia. We used another company transistor and everything works fine. I checked BCX56 on DC supply. It starts leaking as voltage on collector increased above 30V. Surprisingly, the datasheet says VCEO = 80V; that's why it was ordered.

0 Caleb Perez over 3 years ago in reply to Nick

TI__Genius 11315 points

Got it, glad it was figured out!

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BQ76952: Problem as soon REG1 switched on