LM5165: X suffix - Output not reaching 5V

Sean Brown

Part Number: LM5165

Hello,

I have created a PCB using the schematic proposed on Webench. I have shorted RT to ground for PFM operation and shorted SS to ground.

L1 = 150uH, Cin = 1uF, Cout = 10uF.

I have not included Rseries.

The voltage does not increase beyond 1 volt.

Can anyone tell me what I need to check to isolate the issue?

Kind regards,

Sean

over 6 years ago

0 Sean Brown over 6 years ago

Prodigy 60 points

Would shorting the SS pin to gnd cause this problem?

I have already cut the track and added an ESR resistance, which did not help

0 Samuel Jaffe over 6 years ago in reply to Sean Brown

TI__Mastermind 25590 points

Sean,

SS should have a cap to GND or be left floating. Please share your WEBENCH design if WEBENCH recommended connecting SS to GND.

If this does not fix your issue, please share the full schematic and the layout.

Thanks,
-Sam

0 Sean Brown over 6 years ago in reply to Samuel Jaffe

Prodigy 60 points

hello Sam,

This is not an easy fix to attempt due to my track layout.

WEBENCH did not recommend the SS to GND. I originally intended it to float and am not sure why it is grounded now.

I'll attempt the correction and see if it helps

Thanks

0 Samuel Jaffe over 6 years ago in reply to Sean Brown

TI__Mastermind 25590 points

Sean,

Let me know what you find.

-Sam

0 Sean Brown over 6 years ago in reply to Samuel Jaffe

Prodigy 60 points

Thank you, Sam,

Floating the pin fixed the issue. It was a harder fix than I had hoped for, but easier than I expected once I had the technique down.

Power management

Power management forum

LM5165: X suffix - Output not reaching 5V