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TPS51200: TPS51200 / REFOUT and VO startup waveform at tracking configuration

S.Satoshi
Guru 21675 points
Part Number: TPS51200

Hi,

Now my customer consider to use TPS51200 and then they found that REFOUT and VO seem to startup with non-linearly in typical timing diagram as below. So Can you provide actual startup waveform of REFOUT and VO at tracking configuration for their reference? I'm asking it because I can't find reference waveform in datasheet and user's guide.

Best Regards,

Satoshi / Japan Disty

  • 0
    TI__Mastermind 24075 points
    Hi Satoshi,

    The actual waveform of REFOUT and VO is similar with the waveform in datasheet timing diagram.
    When REFIN voltaga is lower than 0.39V, REFUOT and VO is 0V.
    Once REFIN rises up to 0.39V, REFOUT and VO follow REFIN.

    What is customer application, DDR3, DDR4 or else?

    Thanks
    Qian
  • 0 in reply to Qian Chen
    Guru 21675 points

    Hi Qian,

    My customer consider to use TPS51200 for DDR3L. Now they are evaluating it and then they found voltage spike during REFOUT start-up as below. They tried to use 4.7uF capacitor between REFOUT and GND and then this voltage spike was removed. So please give your comment for following question.

    [Question]

    Can you recommend to use capacitor on REFOUT larger than 0.1uF? Do you have any concern when they use 4.7uF on REFOUT?

    Best Regards,

    Satoshi

  • 0 in reply to S.Satoshi
    TI__Mastermind 24075 points

    Hi Satoshi,

    I will check with team if 4.7uF cap on REFOUT is fine.  

    Meanwhile, can you ask customer to check if REFOUT dip is caused by REFIN? Please probe REFIN pin voltage.

    Also, can you check if the REFOUT dip is caused by DIMM. If it is possible, disconnect REFOUT from DIMM and check again.

    Thanks

    Qian

  • 0 in reply to Qian Chen
    Guru 21675 points

    Hi Qian,

    Thank you for your support.

    I have the schematic but I can't share it on E2E because this is provided from customer. But actually REFIN is divided from VLDOIN so there is no dip on VLDOIN and REFIN as waveform I provided.

    Regarding inrush current, I share additional waveform that is measured with 0.1uF. The inrush can be seen but this is not cause of the dip.

    Best Regards,

    Satoshi

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

    Can you send the schematic in pdf file and all test waveforms to: Q-CHEN@TI.COM?
    Let me check schematic first.

    Thanks
    Qian