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TPS613221AEVM: Backfeeding TPS613221ADBVT with parallel source

Andrew Mowry
Prodigy 90 points
Part Number: TPS613221AEVM
Other Parts Discussed in Thread: TPS61322

I asked this about another converter, but I wanted to make sure it's okay for this one as well.

Is it okay to backfeed the OUT pin with a 5.0V parallel source, both when there is an input voltage on the SW pin and when it is disconnected?

Will the converter conduct current in reverse when I do this?

Thanks!

  • 0
    TI__Expert 7485 points

    Hi Andrew,

    What is your 5 parallel source? Is it also a boost?

    TPS61322 doesn't have true disconnection, so it is like you connect a inductor and a diode parallel with the 5V source.

    So if the VIN < VOUT, diode will not conduct, I think this would be no problem.

    If the VOUT > target VOUT of TPS61322, also no problem.

    If the VOUT < target VOUT of TPS61322, device will switch and there may be some abnormal behavior. 

    Regards,

    Nathan

  • 0 in reply to Nathan Ding
    Prodigy 90 points

    Great, thank you. The 5V source is USB. I hope to connect it without having to worry about disconnecting the battery (single cell NiMH) from the converter. Part of my concern was that if the battery voltage was very low it might be out of spec to have a parallel source on VOUT. VOUT will always be higher voltage than VIN, so it sounds like this will be fine. As you saw in my other question, I'm also considering other converters with an EN pin (like the TPS610994), but I assume the behavior is similar for all of these, i.e. they can all handle a parallel source on VOUT that is higher than VIN?

  • +1 in reply to Andrew Mowry
    TI__Expert 7485 points

    Hi Andrew,

    For TPS610994, if EN is high, the results will be as same as what I have said above. If EN is low, because of true disconnection this device has, there will be no path between VIN and VOUT, so it sill no problem regardless of VIN VOUT.

    Regards,

    Nathan

  • 0 in reply to Nathan Ding
    Prodigy 90 points

    Perfect, thanks again.