LTC3554

I use the LTC3554. I switch it On with a High on PWR_ON and OFF with Low at this PIN. With my first Boards I have no Problems. With the Production Boards from a other manufacture the LTC3554 didn’t switch On with a High at PWR_ON.

On/Off with the ON-Pin is OK on both Boards.

The wiring at the LTC3554 is on both Boards the same.

The marking on the LTC3554 is different:

918

LDYS

B112

 

And

 

834

LDYS

B436

 

Have you some Idea what was wrong ?