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TPS22912C: Rerverse current protection when both input voltages are about equal.

Denis Alain1
Intellectual 600 points
Part Number: TPS22912C
Other Parts Discussed in Thread: TPS2116, TPS2121

Hi,

We have 2x TPS22912C connected in "Y" (both outputs shorted together). The inputs comes from 2x different PCs (5V from USB HOST). The common outputs are used to power some devices. Since there is a full time reverse current protection, can we keep both TPS22912C always ON to use them as an ideal diode?

Looking at the reverse current protection section inside the datasheet, it is stated that it can have a small amount of reverse current before the device is turning OFF. Since VRCP = 54mV and assuming a source impedance of 1 Ohm (a 3FT USB cable has at least 1Ohm), I should expect a reverse current of 54mA max. Is-it right?

Any comments are welcome.
Best Regards,

Denis Alain, Eng. 

  • 0
    TI__Mastermind 32650 points

    Hi Denis,

    The voltage threshold for registering a reverse current event is 54mV but the device is internally measuring the voltage at the IN pin and voltage at the OUT pin.

    It has no reference for the voltage at the power source. This means that 54mV has to be dropped in reverse across the Power FET (internally). 

    Assuming that you are running this at 5V, your nominal R_on is 60mOhm which means that you will see reverse current events upward of 0.5A before enough voltage is dropped over the FET for it to start blocking.

    If your goal to provide a backup source to the load? If so you can use a device like TPS2116 or TPS2121. These PowerMUXes take two inputs and provide one output depending on user set priority or could be set to always pass the highest voltage. They offer channel to channel conduction prevention.

  • 0 in reply to Shreyas Dmello
    Intellectual 600 points

    Hi Shreyas,

    Our goal was to use this part as true diodes (no FWD voltage drop) to use current from 2x PC at the same time. I understand that the reverse current can be quite high. So we will use them as simple SW instead.

    Best Regards,

    Denis Alain, Eng.