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TPS22990: Use a load switch to prevent output leakage when the input is absent?

John Peck66
Prodigy 100 points
Part Number: TPS22990
Other Parts Discussed in Thread: TPS22953

I'd like to use the TPS22990N to isolate a DC/DC converter from a separate power supply.  Please see the schematic I've pasted below, and the larger version I've attached.  I'm worried that the switch will not have a bias voltage when the barrel jack supply is absent.  It seems like current will leak back through the switch if there's no bias supply to charge the output MOSFET.  My solution is to provide this bias voltage from the output through a diode.  Will the switch be OK with this?

Barrel_Power.pdf

  • 0
    TI__Genius 13650 points

    Hi,

    Welcome to E2E!

    The issue I see here is not with there not being a bias voltage on the when the barrel jack supply is active, but with the TPS22990 not having reverse current blocking capabilities. Without reverse current blocking capabilities the TPS22990 will not block reverse current from flowing from OUT to IN through the body diode of the load switch even if there was a bias voltage. 

    If reverse current blocking is needed with the TPS22990 I would suggest placing two of these devices in series. An example of this is shown in the figure below with a different 2 channel device, but also applies to the TPS22990.

    A different option would be the TPS22953 which has lower current capabilities than the TPS22990, but this device offers reverse current blocking when the device is off and no voltage needs to be supplied to the VBIAS.

    Let me know if there's any questions about either of the 2 solutions proposed

    Best regards,

    Andy Robles

  • 0 in reply to Andy Robles
    Prodigy 100 points

    Thanks.  Exactly what I needed to know.