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LM5164: Protection against reverse voltage required?

Michael Sprick
Prodigy 10 points
Part Number: LM5164

Hi there,

this is probably more of a general question regarding switching power supplies... or maybe it is indeed part specific. Not sure ;)

I'm using the LM5164 for many of my boards where I need buck converters to step down from 48-80V to 5V.

In order to be able to program the micocontroller, some boards have an ISP oder debug connector on them.

Thus, a USB programmer can also directly supply the 5V rail through the ISP connector.

Now I was wondering... do I have to protect the LM5164 against "reverse voltage" by placing a diode right behind it?

Imagine the 48V main supply was disconnected and the LM5164 was inactive, but 5V rail was supplied via ISP...

Looking forward to your thoughts! Thanks ahead.

  • 0
    TI__Expert 8130 points

    Hi Michael,

    Yes, I recommend to place a diode at the output. I believe that is what you meant by "by placing a diode right behind it?". Reverse current happens when there is a higher voltage at the output of a system than at the input.

    For instance, in the example you mentioned of removing the input source would result in "reverse current". Reverse current can travel backwards through the MOSFETs body diode if it becomes forward-biased, because the FET output voltage is greater than the input voltage.

    Regards,
    Alejandro