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LMX1204: configuration of LMX1204 and LMX2820

Shinichi Inoue
Guru 20031 points
Part Number: LMX1204
Other Parts Discussed in Thread: LMX2820

Tool/software:

Dear Specialists,

My customer is considering LMX1204 and LM2820 for JESD204B CLK.

They have questions, I would be grateful if you could advise.

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We have questions regarding LMX2820 and LMX1204. 

Could you please advise?

I want to generate four 3.2GHz signals for ADC, two 6.4GHz signals for DAC, one JESD204B SYSREF (6.25MHz), one LOGICCLK (200MHz) and one LOGICSYSREF (6.25MHz) signal.

Q1: Is it possible to output different frequencies from RFOUTA and RFOUTB of LMX2820?

Q2: The receiving side (RFSoC) has one SYSREF input, and the RFSoC's built-in ADC: 8ch and DAC: 8ch share one SYSREF input. The LMX1204 has a SYSREFOUT for each CLKOUT, but is it okay to use any SYSREFOUT?

Q3: The LMX2820 does not have an input port for the SYNC signal.
I connected the SYNC signal to the SYSREFREQ pin of the LMX1204, and configured the LMX2820's SYSREF output (SROUT pin) not to be used.
Is this no problem?

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I appreciate your great help in advance.

Best regards,

Shinichi

  • 0
    TI__Guru* 86030 points

    Hi Inoue-san,

    LMX2820 can support 3.2GHz and 6.4GHz output at the same time.

    The SYNC signal to LMX2820 should go to the PSYNC pin (pin 5). 

    Outputs from LMX1204 are identical, you can use any of the CLK and SYSREF outputs.

  • 0 in reply to Noel Fung
    Guru 20031 points

    Hi Noel,

    Thank you for your reply.

    I'll share your answer with the customer.

    when the customer has an additional question, I consult you again.

    Best regards,

    Shinichi

  • 0 in reply to Shinichi Inoue
    Guru 20031 points

    HI Noel,

    The customer has an additional question.

    Could you please advise?

    --

    According to you answer, the SYNC signal should be connected to the PSYNC pin.


    I understand to connect the SROUT P/N (SYSREF) of the LMX2820 to the SYSREFREQ P/N of the LMX1204,
    and also connect one of the SYSREF outputs of the LMX1204 to the RFSoC?

    Is my understanding correct?

    I appreciate your great help and cooperation.

    best regards,

    Shinichi 

  • 0 in reply to Shinichi Inoue
    TI__Guru* 86030 points

    Hi Inoue-san,

    That is correct. 

    LMX1204 can generate SYSREF signal (continuous clock or pulses), you can also use it, instead of LMX2820 to generate the SYSREF signal. 

    Which device to generate SYSREF is up to customer's planning, both devices can do the job. 

  • 0 in reply to Noel Fung
    Guru 20031 points

    Hi Noel,

    Thank  you for your reply.

    I'll share your answer with the customer.

    If the customer has an additional question, I consult you again.

    I appreciate your great help and cooperation.

    Best regards,

    Shinichi