LM25117: No output, what's different between webench and evm?

Che yi Su

Part Number: LM25117

We followed TI webench tool to designed LM25117, input is 18 to 26V and output is 16V/7A. The resault is no output during test, and we found schematic is different between webench and EVM. Could you help me to chech what's wrong value or circuit to let no output?

My schematic:

Webench:

EVM:

over 6 years ago

0 Samuel Jaffe over 6 years ago

TI__Mastermind 25590 points

Che yi Su,

I will take a look at these schematics. I can say WEBENCH is probably not going to have the same schematic as the EVM since WEBENCH is made to fit your specs. The EVM is made to fit a single common spec.

Do you have some test/debug data? Does FB have a voltage on the no-output board? Does VCC come up?

-Sam

0 Che yi Su over 6 years ago in reply to Samuel Jaffe

Expert 1695 points

We try to change IC from evm to my board, and evm still work fine. Try to change UVLO point to lower by remove resistor to ground. The FB pin is not short or open. We found evm VCC and RAMP design are different. Is it reason to cause no output?

0 Samuel Jaffe over 6 years ago in reply to Che yi Su

TI__Mastermind 25590 points

Che yi Su,

Try replacing your R5 from 10 ohms to a short circuit.

Please share waveforms at startup of:

VIN at the IC
FB
COMP
SW
HO
LO

Please also share the layout.

-Sam

Power management

Power management forum

LM25117: No output, what's different between webench and evm?