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TPS51206: Power on sequence

Kei Kuwahara
Expert 4920 points
Part Number: TPS51206
Other Parts Discussed in Thread: TMDS64EVM, TPS51200

Hello team,

I am confused on power on sequence of this device.

On datasheet 7.3.6, it says "During power on, it is allowed to turn on VDD, S3 and S5 first, then turn on VLDOIN and VDDQSNS."
However, on Figure 23, it looks like VLDOIN and VDDQSNS is powered up before S5 and S3.

Which line should I power up first?

On the schematic of TMDS64EVM (PROC101D(004)), looks like S3 and S5 is powered up at the same timing. Also VDD and VLDOIN is powered up at the same time.

Is it okay to power up S3 & S5 and VDD & VLDOIN at the same timing?

What is the correct power up sequence for each power lines?

Best Regards,
Kei Kuwahara

  • +1
    TI__Genius 10692 points

    Hi Kei,

    The recommendation is to follow the typical timing diagram with VDD -> VLDOIN  + VDDQSNS -> S5 -> S3. 

    But you are also able to utilize VDD, S3 and S5 -> VLDOIN + VDDQSNS. This is helpful when inputs are tied together, similar to the schematic you have shown above.

    However, VDD should come up before VLDOIN.

    Thanks,
    Field

  • 0 in reply to Field Tolson
    TI__Expert 4920 points

    Hi Field-san,

    Thank you for your quick answer!

    What about powering up VDD and VLDOIN at the same time?
    On the schematic of TMDS64EVM (PROC101D(004)), looks like VDD and VLDOIN is powered up at the same time.

    Best Regards,
    Kei Kuwahara

  • +1 in reply to Kei Kuwahara
    TI__Genius 10692 points

    Hi Kei,

    Field Tolson said:
    However, VDD should come up before VLDOIN.

    As mentioned earlier, VDD should come up before VLDOIN. This is also the recommendation for this device, and similar devices like the TPS51200. 

    This power sequence may lead to abnormal waveforms on startup or more Such an example may be overshoot or others.

    Thanks,
    Field