TPS54540: Vin will be pulled down to 4V when the load is high above 0.7A

Yang RuoFei

Prodigy 10 points

Part Number: TPS54540

Tool/software:

attach the schematic. the issue is:

when the load is less than 0.7A, the Vout is working normally.
when the load is higher above 0.7A, the Vin will be pulled down to 4V, lead Vout can not output normally.

please help to analyze what problem is?

2 months ago

0 Onkar Bhakare 2 months ago

TI__Genius 14676 points

Hello Yang

How are you powering up the converter? Is it through some power supply. If yes, set its current limit to 2.5A or higher and check if issue still persists

Thank you

Regards

Onkar Bhakare

0 Yang RuoFei 2 months ago

Prodigy 10 points

power supply is 28V input，EN pin is connect a ULVO protection circuit. as i know, this chip have no current limit feature. how to set current limit?

0 Yang RuoFei 2 months ago

Prodigy 10 points

from Oscilloscope waveform show, the 28V power have been pulled down to under low voltage threshold--->EN pin lower than 1.1V---->chip disabled--->power resume----->chip enable: always cycle to cycle.

0 Onkar Bhakare 2 months ago in reply to Yang RuoFei

TI__Genius 14676 points

Hello Yang

This typically happens under two scenarios

Insufficient power supply current limit: The 28V power supply might not be able to provide enough current to support the load, causing the voltage to drop.
UVLO circuit interaction: The UVLO circuit might be interacting with the chip's enable circuitry, causing the chip to disable and re-enable repeatedly.

Could you please share UVLO circuit you were mentioning. As I only EN is being driven externally

Thank you

Regards

Onkar Bhakare

+1 Onkar Bhakare 2 months ago in reply to Onkar Bhakare

TI__Genius 14676 points

Hello Yang

Any updates on this?

Thank you

Regards

Onkar Bhakare

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TPS54540: Vin will be pulled down to 4V when the load is high above 0.7A