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TPS549D22: Power down behavior, PVIN is under 1.5V but VDD is over 4.5V

Oba
Genius 17325 points
Part Number: TPS549D22

Hello

 

I have a question about PVIN specification of TPS549D22.

The datasheet defines that “recommended operating conditions” of PVIN is 1.5 – 16V.

For VDD, it is 4.5-20V. VDD has UVLO function, but PVIN doesn’t have UVLO.

 

During shutdown, the system requires TPS549D22 continue to output(around 1-1.2V) as long as possible.

In this case, VDD voltage can be kept over 4.5V relatively long time, but PVIN voltage can’t.

 

What will happen if VDD is over 4.5V but PVIN is under 1.5V?

My expectation is keeping output as far as possible.

 

Regards,

Oba

  • 0
    TI__Genius 17325 points
    Hello,

    Could anybody support?

    Regards,
    Oba
  • 0 in reply to Oba
    TI__Guru**** 191445 points
    Let me see what I can find out. It may be next week due to US holiday. Also we probably do not have that specific data. The lower PVIN limit is somewhat arbitrary. Eventually if you are drawing enough current you will have enough drop that your duty cycle tends towards the maximum. So you should be able to allow PVIN to drop below 1.5 V and keep switching, but eventually you will run out of headroom and the output will fall out of regulation.