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LM5050MK-1EVAL Oring problem

Alex Akerman
Prodigy 10 points
Other Parts Discussed in Thread: LM5050-1

Hello,

I`m using LM5050-1 for Oring FET controller.

In evaluation board I see the problem with LM5050 OFF signal.

i conected power supply with VIN 12V, Vout  is also 12V , even I connect to OFF TP voltage 2-5V.

When OFF signal connected to 0V the Gate voltage is 23V, when I connect 5V (expected Vout=0V) to OFF TP, the Gate voltage is 12V and Vout is 12V.

Thanks,

Igor

  • 0
    TI__Expert 5940 points
    Alex
    "Off" turns off the FET. It shorts gate to source through the transistor in the center of the block diagram on page 9 of the data sheet. So, gate voltage will = 12v but gate-source = 0v and the FET is off. The body diode of the FET is still in play and Vout will remain close to Vin less the forward drop of the diode. Vout will not drop to 0v as the device +FET now looks more like a traditional ORing diode rather than the FET pass element.
    Brian