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LMH1983: What instance is the PLL3 reset in the Initialization process?

user4779049
Expert 2375 points
Part Number: LMH1983


Hi Team,

Please advise me two questions bellow.

The LMH1983 datasheet “8.3.11.1 TOF3 Initialization Set Up” insists that it is
recommend setting PLL3 into “Always Align mode” to firmly Reset PLL3.

Q1. When the PLL3 is reset?
Does the PLL3 reset at top of frame 1 (TOF1) or top of frame 3 (TOF3)?

Q2. When 10 MHz, 27 MHz, 96kHz, 48kHz, 44.1kHz 32 kHz or unknown video is
Applied to the REF input, how much the period of FOUT1?

Mita

  • 0
    TI__Mastermind 32575 points
    Mita-san,

    1. PLL3 and TOF3 are reset together by setting TOF3 in Always Align mode. After PLL3 is reset/initiallized, set TOF3 alignment mode should be set back to Never Align mode.

    2. TOF1 is not applicable to these clock inputs you listed, since there is no input frame pulse associated with these input timing formats.

    Alan
  • 0 in reply to Alan O
    Expert 2375 points

    Alan-san,


    Thank you for the answer.
    Please allow me further question.

    I don’t think PLL3 is reset immediately after the register 0x13 bit [5:4]=’10b is written
    to make PLL3 is set into ‘Always Align mode.

    Because, in order to align TOF3 to TOF1, TOF3 reset shod be performed on the top of Frame 1 (TOF1).
    How TOF3 is aligned to TOF1 without knowing the top of Frame 1?

    Mita

  • 0 in reply to user4779049
    TI__Mastermind 32575 points

    I don't really follow your comment or concern.  What is the specific problem you are observing?

    Are you saying PLL3 or TOF3 is not being reset when the input format is a clock without Vsync or Odd/even Frame pulse (like 27M, 10M, audio clock)?

    Alan

  • 0 in reply to Alan O
    Expert 2375 points

    Alan-san,

    Sorry for making you confused.

    My question is how long do you need to wait after you set the PLL3 in “Always align mode” at initialization process.
    I want to set the device in Never Align mode after completing the initialization process.
    (I do not experience any trouble but want to know proper use case of the device)

    If PLL3 is reset immediately after set into Always align mode, it can be switched back to Never Align mode instantly.
    If PLL3 is reset within 1080p59.9 frame regardless of input format, it can be wait for at least 66 ms.

    Which is proper procedure?

    Mita.

  • 0 in reply to user4779049
    TI__Mastermind 32575 points

    You should wait for TOF3 frame counters to terminate/reset and generate a TOF pulse before switching back to never align mode.

    Alan

  • 0 in reply to Alan O
    Expert 2375 points

    Alan-san,

    Thank you. I got it.

    Mita