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TLC2558: SCLK frequency

K.Yaita
Guru 29710 points
Part Number: TLC2558

Hi Team,

The SCLK frequency is 10MHz for his system.
I believe 10MHz is no ploblem but tWL and tWH shows 30ns (MAX) in datasheet.



Should these specification (tWL, tWH) consider under 20MHz condition?
I would also like to know why there is maximum value (30ns) for these specification.

Best Regards,
Yaita / Japan disty

  • 0
    TI__Genius 16890 points
    Hi Yaita-san,

    Please see Figure 16 in the datasheet. These two specifications show the minimum amount of time that the SCLK signal should be high or low. If the SCLK is running at 20MHz, that gives 50ns for a clock cycle. When the high and low are at 20ns each, that leaves 10ns for the rise and fall time.
    I am not sure why there is a max spec of 30ns. If you had a clock signal running with 30ns high and low, the fastest the clock could be is 16.6MHz.

    Mike
  • 0 in reply to Michael Stout
    Guru 29710 points

    Hi Mike-san,

    Thank you for your reply.

    >I am not sure why there is a max spec of 30ns. If you had a clock signal running with 30ns high and low, the fastest the clock could be is 16.6MHz.
    My customer wants to know if SCLK=10MHz is applicable or not.
    It may exceed 30ns (MAX) of tWL or tWH when SCLK=10MHz, it is the background of the question.

    Best Regards,
    Yaita

  • 0 in reply to K.Yaita
    TI__Guru**** 173636 points
    Hi Yiata,

    The twL and twH minimum and maximum times are setting the duty cycle limits (60/40) on the SCLK assuming a MIN clock period of 50nS. You can use a 10MHz clock so long as you adhere to the 60/40 duty limitations.