BQ76952: BQ76952 LDO output power consumption is large, and the external NPN generates heat

Star Xu

Part Number: BQ76952

The customer design with BQ7695202 (default output LDO1) According to the reference design, the circuit has a standby current of 10mA when powered on at 50V.

After disconnecting the 3.3V output of REG1, the standby current is close to 0mA.

The actual load current under test REG1 is 10mA at 3.3V. The input B+ B- power consumption is 10mA (50V). The NPN transistor generates heat.

NPN transistor model: FCX495TA

Please help check it.

Thanks

Star

8 months ago

0 Luis H. S. 8 months ago

TI__Mastermind 35260 points

Hello Star,

Yes, the NPN will generate heat as the voltage is stepped down and the more current is flowing through it, that's normal. The resistors on the collector are meant to help the BJT to not have to handle the whole stack voltage.

Best Regards,

Luis Hernandez Salomon

0 Star Xu 8 months ago in reply to Luis H. S.

TI__Genius 9645 points

Hi Luis

Thanks for your help.

The power consumption of the NPN buck circuit is large. Is it necessary to use an external DC-DC to reduce power consumption?

Waiting for your reply.

Thanks

Star

0 Luis H. S. 8 months ago in reply to Star Xu

TI__Mastermind 35260 points

Hello Star,

It is US. holidays, expect a response by Wednesday 2/21.

Regards,

Luis

0 Luis H. S. 7 months ago in reply to Star Xu

TI__Mastermind 35260 points

Hello Star,

You do not need to use a BJT for this step-down circuit, if desired an external supply (Such as a buck converter to REGIN) can be used to deliver power to REGIN. Follow the datasheet recommendations for how to connect REGIN and BREG (Read Section 16.6 Unused Pins of the datasheet)

Best Regards,

Luis Hernandez Salomon

Power management

Power management forum

BQ76952: BQ76952 LDO output power consumption is large, and the external NPN generates heat