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DAC088S085: Tss/Tsh specifications

Yusuke Mukuno
Expert 7395 points
Part Number: DAC088S085


Hi expert,

My customer have a question for the Tss/Tsh specifications.

Tss maximum spec is 1/fsclk -3 (ns)

Tsh maximum spec is 1/fsclk -3 (ns)

Does they have to meet the specification even if not continuously SCLK as below?

Blue : SYNC, Pink : SCLK

Tss=310ns

SCLK frequency is 5.1MHz. Therefor, 1/fsclk -3 (ns) = 193(ns)

Thanks

Muk

  • 0
    TI__Mastermind 19096 points

    Hi,

    SYNC falling to SCLK falling edge (set up time) has to be maintained whether you are giving continuous SLCK or not. Similarly for SYNC hold time after the 16th falling edge of SCLK.

    You should have min 10ns for set up time (tss). I mentioned 10ns instead of 3ns for the entire operating temperature range.

    Regards,

    AK

  • 0 in reply to Akhilesh K
    TI__Expert 7395 points

    Hi AK-san

    Thank you for your answer.


    is it meaning,  the SCLK falling edge need between 10ns and 1/fsclk-3(ns) from SYNC?

    Why does the maximum spec is depend on fsclk?

    Thanks

    Muk

  • 0 in reply to Yusuke Mukuno
    TI__Mastermind 19096 points

    Hi Muk,

    To avoid mis-clocking data into the shift register, it is critical that SYNC not be brought low on a falling edge of SCLK. From this, the requirement is derived that max set up time is a function of SCLK. Similarly, on the 16th falling edge of SCLK, the last data bit is clocked into the register. The write sequence is concluded by bringing the SYNC line high.

    Regards,

    AK

  • 0 in reply to Akhilesh K
    TI__Expert 7395 points

    Hi AK-san

    I would like to exactly confirm about your comment below,

    >To avoid mis-clocking data into the shift register, it is critical that SYNC not be brought low on a falling edge of SCLK

    If Tss> 1/fsclk, SYNC will be brought low on a falling edge of SCLK by the previous clock as below,

    Is my understanding is correct?

    My question is for in case of not continues SCLK.

    if SCLK is not continues like as customer waveform, the SYNC not be brought low on a falling edge of SCLK.

    Is it OK or NG?

    Blue : SYNC, Pink : SCLK

    Tss=310ns from waveform

    SCLK frequency is 5.1MHz. Therefor, 1/fsclk -3 (ns) = 193(ns)

    Tss > 1/fsclk -3 (ns)

    Does the customer waveform have any problem?

    Thanks

    Muk

  • 0 in reply to Yusuke Mukuno
    TI__Mastermind 19096 points

    Hi Muk,

    Your understanding is right.  If it is not continuous SCLK, like your customer, is doing, no issues of exceeding the max limits specified in the datasheet.

    Only make sure that SYNC is not brought low in the falling edge of SCLK.

    Regards,

    AK

  • 0 in reply to Akhilesh K
    TI__Expert 7395 points

    HI AK-san,

    Thank you for your answer!!

    Muk