I am testing the L7987L chip for my PoE module project. I got the dev board STEVAL-ISA198V1.I noticed that it gives out 4.8V instead of 5V (with or without load). Also I was expecting that chip will cut output once the input voltage is less than 5V (or some other lower threshlod, not important), but it is still "leaking". F.eg If in input is less than 5V (3V,2V...), my expectation is 0V on output, however I still see 1-2V on output pins, which is useless power in my case.I have also build PCB as per gerber files, and it has same behavior.I checked my Fluke multimeter against the power generator - it is correct, so multimeter calibration is fine.Is this an expected behavior?ThanksSergi

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Question

L7987L switching regulator, does not output expected voltage

I am testing the L7987L chip for my PoE module project. I got the dev board STEVAL-ISA198V1.

I noticed that it gives out 4.8V instead of 5V (with or without load).
Also I was expecting that chip will cut output once the input voltage is less than 5V (or some other lower threshlod, not important), but it is still "leaking". F.eg If in input is less than 5V (3V,2V...), my expectation is 0V on output, however I still see 1-2V on output pins, which is useless power in my case.

I have also build PCB as per gerber files, and it has same behavior.

I checked my Fluke multimeter against the power generator - it is correct, so multimeter calibration is fine.

Is this an expected behavior?

Thanks

Sergi

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