This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

LMR10510 efficiency issue

My customer asks:

We have a load at 3v3 that takes from about 100mA to about 400mA, depending on what’s turned on.

We’re trying to step down from USB input, so a nominal 5v0, but ranging from 4v5 to 5v5.

 

Trying it out at the low end of the load, I had a load current of 136mA, and a source current of 130 mA with a 5v0 input.  This gives me an efficiency of about 75%, when the data sheet would make me expect something in the low 90’s.

 

Circuit is very straight forward, pretty much right out of the data sheet.

 

LMR10510XMF

catch diode: MBRS2040LT3G (ONSemi)

Inductor: SRN4018-3R3M (Bourns)

2x 10uF ceramic input cap

2x 10uF ceramic output cap

 

Any ideas why I’m seeing such poor results?