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TPS7H1101A-SP: Vout behavior when Vin<=Vout(set)

Brian Giesinger22
Prodigy 50 points
Part Number: TPS7H1101A-SP

Hello -

When Vin < Vout(set), how does Vout behave?  For instance, if I have the regulator set to provide 3.3V and Vin<=3.3V, does Vout track Vin?  If so, how close is the tracking, and is it load-current dependent?  My application cannot guarantee that Vin stays greater than Vout(set)+Vdropout, so I am trying to evaluate how the regulator behaves.  Do other functions behave appropriately in this condition? (e.g. current limit, shutdown, etc.).

Thank you,

Brian

  • 0
    TI__Mastermind 20045 points
    Hello Brian,

    Sorry for the delay. I am looking into this and will get back to you soon.

    Thanks,
    Kyle
  • 0 in reply to Kyle Rakos
    TI__Mastermind 20045 points
    Hello Brian,

    I have another question for you - were you asking what will happen when it is just slightly below 3.3V (but still above the minimum 1.5Vin) or were you concerned what happens as it goes from 0 to 3.3V? If I can better understand the concern on your end I can better figure out how to continue my investigation.

    Thank you,
    Kyle
  • 0 in reply to Kyle Rakos
    Prodigy 50 points

    Hello Kyle -

    I am mostly interested in how the regulator behaves when Vin is just slightly below 3.3V (but still above the minimum 1.5Vin).  Is the output voltage equal to Vin, or equal to Vin-Vdropout, or some other value?  Do things like shutdown, current limit, and current sensing still operate properly in this condition, etc?

    What happens on the ramp-up is of secondary concern, more for just a complete understanding of the regulator.

    Thank you,

    Brian

  • 0 in reply to Brian Giesinger22
    TI__Mastermind 20045 points
    Hello Brian,

    Sorry for the delay. I think I now have an answer for your question. When Vin is less than 3.3V (but above 1.5V Vin minimum) it will track the input less a dropout. Current limits and sensing will still function although the accuracy may not be as good as in normal operation.

    As far as operation less than 1.5Vin, we do not have as much information since this isn't where the part is intended to operate. There is no UVLO in this device.

    Thanks,
    Kyle