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DS90CR287 - TxIN Setup/Hold time to TxCLK IN

Kawai
Guru 19785 points
Other Parts Discussed in Thread: DS90CR287

Hello Team,

Please allow me to ask you a question about the Setup and Hold time.

I found the specification in the datasheet which is below. The test condition is for f = 85 MHz.


[Question]
In the case of f = 20 MHz, can you still say that the minimum required setup and hold time is the same ?
TSTC = 2.5ns (MIN)
THTC = 0ns (MIN)

Thanks in advance.

Best Regards,
Kawai

  • 0
    Guru 19785 points
    Hello Team,

    Could anybody help us on this question ? Our customer needs to fix their design soon.
    Your prompt reply is greatly appreciated.

    Best Regards,
    Kawai
  • 0 in reply to Kawai
    TI__Mastermind 29655 points
    Hi Kawai-san,

    Sorry for the delay in response. I researched through some of our characterization data and was able to find some relational data we took for the DS90CR287 TSTC and THTC time when varying frequency. The minimum amount of setup time for this transmitter actually is not fixed. It scales approximately linearly. Unfortunately, the characterization data I found does not have an explicit test for operating at 20 MHz. However, I have seen some trend graphs based on data observed at frequencies down to 37 MHz. Using the approximate linear equation derived from our characterization data, the setup increases as operating frequency decreases by approximately -0.0088 ns/MHz. Taking this equation and extrapolating, if the minimum setup time at 85 MHz is 2.5 ns, then the estimated minimum setup time at 20 MHz is 3.1 ns. If your customer's source minimum setup time for data v. clock into the DS90CR287 at 20 MHz is greater than 3.1 ns, there should not be issues with the design.

    Thanks,

    Michael
  • 0 in reply to Michael Lu (Santa Clara)
    Guru 19785 points

    Hello Michael-san,

    I greatly appreciate for your support!!

    Actually, our customer will use with 37.125MHz, however, I will tell them to design using TSTC=3.1ns(MIN), THTC=0ns(MIN) for their application.

    Best Regards,
    Kawai