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LM5050-1: Conditions for turning off the FET

Dice-K
Mastermind 7470 points
Part Number: LM5050-1

Hi support team,

I think that the FET will be turned off when Vsd(rev) becomes -28mV(typ).

In the case of FET with ON resistance of 10mΩ,
-28mV / 10mΩ = -2.8A

Is the FET not turned off unless the reverse current flows 2.8A?

I make an OR-ing for AC/DC output and battery output.
When AC/DC stops and switches to battery supply, 2.8A does not flow to the AC/DC side, and I think that the LM5050 does not turn off the FET.

In this case, do I use the OFF-pin to turn off the FET?

Regards,
Dice-K

  • 0
    TI__Guru 57737 points

    Hi Dice-K,

    When AC/DC stops, the voltage on the IN of LM5050 drop to 0V. Since the OUT is powered from Battery, the voltage at OUT doesn't  droop. This will create a voltage difference across Source and Drain of the FET and the LM5050 will automatically turn OFF.

    Do you suspect that -ve current wouldn't flow from OUt to IN ? Wouldn't there be some -ve current flowing in the FET back into the capacitance at the output of AC/DC ?

  • 0 in reply to Praveen GD
    Mastermind 7470 points

    Hi Praveen,
    Thank you for your reply.

    I have understood that the GATE voltage is adjusted according to the IN and OUT voltages.

    Best regards,
    Dice-K