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DS90UB941AS-Q1: Initialization sequence

yuichi tanaka
Prodigy 20 points
Part Number: DS90UB941AS-Q1

Two sequence "Sequence A:" and "Sequence B:" are described in DS90UB941 Datasheet "10.2 Power-Up and Initialization".
I can see that these two sequences have different order about Pixel clock input and PDB assert.
However, I do not know the characteristics of each sequence. In what situations shoud I use Sequence A: or Sequence B ?
What is the different of uses of the two sequences?

  • 0
    TI__Guru** 103215 points

    Hello Yuichi,

    Either sequence is acceptable to use for 941AS, and primarily depends on user preference. Functionally they will work the same 

    Best Regards,

    Casey 

  • 0 in reply to Casey McCrea
    Prodigy 20 points

    Thank you for an answer.
    I understood that the two sequences are functionally the same.
    I have the following questions in detail. Let me ask you an additional question.

    1．Sequence A
    Since t4(Min 0ms) and t2(Min 2ms) are specified as the timings from PDB=H to 941AS-Init, the shortest is 2ms.


    2．Sequence B
    Since t4(Min 0ms) and t6(Min 1μs) are specified as the timing from PDB=H to 941AS-Init, the shortest is 1μs.


    Question 1
    Comparing the two timing pecifications, is it correct that the time until 941AS-Init is shorter for Sequence B?

    Question 2
    I don't know why it takes more time for Sequence A to start entering the Pixel Clock before PDB=H than for Sequence B entering the Pixel Clock after PDB = H until 941AS-Init starts.
    Are there any timing conditions that are not specified in Figure 10-2 and Figure 10-3 in the datasheet?

  • 0 in reply to yuichi tanaka
    TI__Guru** 103215 points

    Hello Yuichi,

    t2 is not explicitly shown in sequence B, but it still applies. So there is always a timing constraint between PBD = H and when you can issue the first I2C command to init 941AS (2ms). So it shouldn't really change the init time of the device either way. It would only really make any potential difference if the device is operated in PCLK from DSI clock mode vs. PCLK from external REFCLK mode and only if the REFCLK takes time to power up since you need to have a stable REFCLK before the init sequence is applied. 

    From a practical standpoint, the bottom line is that neither sequence is faster by definition. There may be other system level dependencies which determine init time such as when REFCLK becomes available if you are using PCLK from REFCLK mode, but for other modes such as PCLK from DSI clock mode it doesn't make a difference. 

    Best Regards,

    Casey