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ADS54J54: Input timing for One-shot SYSREF

Part Number: ADS54J54

Hello,

My customer have some questions about SYSREF for ADS54J54.

[Background]

They want to use one-shot SYSREF.

It is written as follows in D/S.

P.28 : ADS54J54 device requires a minimum of 3 SYSREF pulses to complete the synchronization phase. (D/S P.28)

P.32 :  Step7 : Wait for two SYSREF pulses

[Q1]

How many SYSREF pulses does it require, 2 or 3 ?

Does three SYSREF pulse mean "skip one, use all pulses" setting in SYSREF_JESD_MODE_AB/CD, or not ? 

[Q2]

Please tell me the input timing in the JESD204B Interface Initialization Sequence if it require three SYSREF pulses.

Best Regards,

Hiroshi Katsunaga

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  • Hiroshi,

    I am checking with the design team regarding this. Can you ask the customer to explain a little more what they asking for in Q2? Do they want to know the SYSREF frequency, setup and hold info, register write info, ect....?

    Regards,

    Jim

  • Hi Jim,

    Thank you for your fast response.
    OK, I will wait your feedback.

    They want to know the follows in Q2.

    The two SYSREF pulses input timing is described as step 7 in the D/S P.32 7.3.12 JESD204B Interface Initialization Sequence.
    However another SYSREF pulse input timing is not described in the D/S if it require three SYSREF pulses.
    Therefore they want to know the input timing of another SYSREF in the initialization sequence.

    Also they want to know how to choose "SYSREF JESD MODE AB/CD" register value.

    I understand how to choose the SYSREF frequency, setup and hold info, therefore they don't have any problem.

    Best Regards,
    Hiroshi Katsunaga
  • Hi Jim,

    How is the investigation going now?

    Best Regards,
    Hiroshi Katsunaga
  • Hiroshi,

    In step 7, after the JESD block is taken out of the initialization step (after 2 SYSREF pulses occur) a third SYSREF is then required to synchronize the JESD block with the other logic blocks in the device.

    For "SYSREF JESD MODE AB/CD" register value, I would suggest using the default option of skip one SYSREF, then use all.

     Regards,

    Jim

  • Hi Jim,

    Thank you for your clear comments.
    OK, I understood your comments.

    Best Regards,
    Hiroshi Katsunaga