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Original question:

DP83869HM: pulse trans selection

DP83869HM: two supply power up sequence

Kai Nomiyama
Expert 5695 points

Part Number: DP83869HM

Hi Team,

Could you let me know two supply configuration power up sequence?
In datasheet figure 115, we can see two supply sequence diagram.

However, customer power up sequence is like below since 2.5V and 1.1V don't turn up at the same time.

In that case, questions here are
1. Which one should turn up first, 2.5V or 1.1? or there is no restriction?
2. what is t3 time(max)?
3. which one is the starting point of t4? 2.5V or 1.1V? first turn up power or second one?
4. Is it ok to consider that t4 is the same as t2 50ms_max(table 101. two supply sequence)?

Regards,
Kai

  • 0
    TI__Genius 11725 points

    Hi Kai,

    First, to clarify, I believe the bottom supply in the diagram provided should be VDDIO. We will need to double check the restrictions on VDDA2P5 and VDDA1P1 sequencing and get back to you later this week. T3 should be 50ms max, as this is the max time for VDDIO to begin ramping after VDDA2P5/1P1 have ramped. It is ok to consider t4 the same as t2 based on your diagram. Again we will need to get back to you about the sequencing requirements for VDDA2P5/1P1.

    Thank you,

    Nikhil 

  • 0 in reply to Nikhil Menon
    TI__Expert 5695 points

    Hi Nikhil,

    VDDA1P1 is typo.
    You are right, the bottom supply in the diagram is VDDIO.(I updated it).


    I will wait for your reply.
    Thanks!

    Regards,
    Kai

  • 0 in reply to Kai Nomiyama
    TI__Genius 11725 points

    Hi Kai,

    We recommend powering VDDA2P5 and VDDA1P1 at the same time. We have seen POR issues if 1V1 and 2V5 were delayed. Please keep the delay (T3 in your diagram) as minimal as possible, if not 0. T4 in your diagram would begin at the first supply. Please keep this time under 50 ms max as the datasheet describes. 

    Thank you,

    Nikhil

  • 0 in reply to Nikhil Menon
    TI__Expert 5695 points

    Hi Nikhil,

    Here is customer power up sequence.
    VDDA2P5 --> (1~2ms) --> VDDA1P1 --> (less than 10ms) --> VDDIO

    there is 1~2ms delay but is this problem for DP83869HM POR?
    Could you let me know what is the maximum time of VDDA2P5 and VDDA1P1 delay?

    Regards,
    Kai

  • 0 in reply to Kai Nomiyama
    TI__Mastermind 18425 points

    Hi Kai,

    The datasheet requirement is to have the VDDA2P5 and VDDA1P1 to ramp up together, so there should be no delay in the VDDA2P5 and VDDA1P1. 

    -Regards

    Aniruddha