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LM5050-2: Driving back-to-back MOSFETs

Part Number: LM5050-2
Other Parts Discussed in Thread: TPS2410, LM5060

Is there some reason that the LM5050-2 can't drive back-to-back MOSFETs? The datasheets don't show that configuration in any of the examples, so I prefer to get clarification.

I want to implement a back-up supply using an LM5050 on each channel with highest priority given to the AC/DC channel. The DC/DC channel will be switched off at the LM5050 as long as the AC/DC is regulating. I can't afford to have sorting and pairing of AC/DC and DC/DC in production, so in the case where the DC/DC output is higher than the AC/DC output the MOSFET diode would tend to conduct and drain my battery or, at worst, fry the MOSFET diode so I would like to put in a second MOSFET in that channel. Please advise if that is possible.

  • Hi Sean,

    LM5050-2 can not drive back-back MOSFETs because of its gate drive. When device is disabled, LM5050-2 shorts Gate -Source and not Gate - GND.
    This means the second MOSFET will not be OFF fully. It would be acting as a voltage follower, so the output voltage will not drop to 0V.

    Can you consider using TPS2410 if the operating voltage is acceptable?
    What are the power levels required, interms of operating voltage and current range?

    Otherwise, need to place LM5060 additionally in the path to drive the second FET.

    Regards,
    Kari.
  • Hi Kari,

    Thank you for your prompt answer. My application is 48V/8.4A. It looks like I will need an LM5060.

    Best regards,

    Sean Carthy