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TPS53317: Prebias startup capability

S.Satoshi
Guru 21675 points
Part Number: TPS53317

Hi,

The customer has evaluated TPS53317 on their test board right now,but they can see leak voltage on VTT from load (DDR3 memory) before power-up. Then does TPS53317 have prebias startup capability and it can regulate VTT with no anomaly under this condition?

Best Regards,

Satoshi

  • 0
    TI__Mastermind 24075 points

    Hi Satoshi,

    If the prebias voltage is below regulate voltage, TPS53317 should be able to start up.

    Usually the leakage current is small, one workaround solutionis to add bleeding resistor on VTT to keep prebias voltage at low level.

    Thanks

    Qian

  • 0 in reply to Qian Chen
    Guru 21675 points

    Hi Qian,

    Thank you for your comment. I understand that TPS53317 can start up if the prebias voltage is below regulated voltage. Then how about the case that the prebias voltage is above the regulated voltage? Is there the possibility of startup fail?

    Best Regards,

    Satoshi

  • 0 in reply to S.Satoshi
    TI__Mastermind 24075 points

    Hi Satoshi, 

    If prebias is above OV threshold, OV protection will happen when part is turned on. 

    OV protection is latch mode. Please refer to section 7.3.5.3 on datasheet page 15 for more information. 

    Thanks

    Qian

  • 0 in reply to Qian Chen
    Guru 21675 points
    Hi Qian,

    Thank you for your information about OV function. From the datasheet, the OV threshold is 120% x VREFIN. Then I'd like to know when the OV function is active? Because the converter may not start-up under pre-bias condition if the OV function is active when V5IN or REF voltage reach UVLO threshold.

    Best Regards,
    Satoshi
  • 0 in reply to S.Satoshi
    TI__Mastermind 24075 points
    Hi Satoshi

    OVP is enabled after soft-start time is done.
    As logn as the prebias voltage is below OVP threshold, the part should start up, but we still suggest to keep prebias volage low if customer is able to do that.

    Thanks
    Qian