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ADS54J60: SYSREF Signal

JH Shin
Mastermind 7060 points
Part Number: ADS54J60

Hello,

My customer is considering using the ADS54J60 under the following conditions.

  - CLKIN = 1GHz, LMFS = 4211, K=32, JESD204B = 10G

According to SYSREF example in the datasheet, SYSREF is calculated as below.

  SYSREF = LMFC / 2^N = fs / K / 2^N = 1000G / 32 / 2^N = 31.25M / 2^N

1. How should the customer determine the value of N ? Does the user decide the value of N so that SYSREF is between 1 MHz and 5 MHz?

2. When N=3, SYSREF is 3.90625MHz, When N=4, SYSREF is 1.953125MHz.

     Is the calculation correct? Which value do you recommend?

3. Is there a way to select continuous mode and N-shot mode for SYSREF?

Thanks.

JH

  • 0
    TI__Expert 8901 points

    Hi JH,

    1. You are correct, N can be any of the values listed in Table 4, as long as the frequency of SYSREF remains between 1 MHz and 5 MHz.
    2. Your calculation is correct. Slower clock rates are better for alignment purposes, so the 1.953125M may be preferable, but both are within the TI recommended range of 1MHz to 5MHz.
    3. I did not see an option for continuous mode in the datasheet. I will double check and get back to you on this.

    Regards, Amy