TPS92641: there is noise on VLED when power off TPS92641

Frank(EP) Liu

Expert 4830 points

Part Number: TPS92641

hi Sir.,

My customer found an issue at power off. At power off, there is noise close to UVLO voltage.

Zoom in.

CH1: Vout (10V/DIV)

CH2: Iout (2A/DIV)

CH4: Vin (10V/DIV)

If they use higher UVLO hysteresis range, the issue is gone.

can I know why it happens? something wrong in design?

BR,

frank

over 5 years ago

0 Irwin Nederbragt over 5 years ago

TI__Mastermind 28655 points

Hello Frank,

There can be issues when transitioning through the UVLO threshold slowly as you are seeing here. What is the hysteresis being used when this happens and what is it when it doesn't happen? What are the values of all the UVLO resistors?

Best Regards,

0 Frank(EP) Liu over 5 years ago in reply to Irwin Nederbragt

TI__Expert 4830 points

hi Irwin,

I send you the schematic by mail.

They change the R9 from 0 to 20k. Vhys from 4.2 v to 16.97V. The symptom is gone.

by the way, this is for TE cooler. The resistor load is around 3.3ohmn. not sure if it affects.

BR,

frank

0 Irwin Nederbragt over 5 years ago in reply to Frank(EP) Liu

TI__Mastermind 28655 points

Hello Frank,

I'm going to close this since we are communicating via email.

Best Regards,

Power management

Power management forum

TPS92641: there is noise on VLED when power off TPS92641