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LMK04828B output frequency

Itai Eden1
Intellectual 330 points
Other Parts Discussed in Thread: LMK04828, ADC12J4000, LMX2582, LMX2541

Hi,

 

I'm starting to develop a module that incorporate an ADC (JESD204 inteface), FPGA DAC & need a clocking solution.

I wish to use the LMK04828 with a 100MHz input clock to drive the FPGA & ADC12J4000.

The required sampling frequency is 2.7GHz.

I see that the LMK04828B VCO does not  support this frequency:

2370 to 2630 MHz & 2920 to 3080 MHz.

Is that correct?

Do you have any suggestion as to how to overcome this limitation?

 

Regards,

Itai

  • 0
    TI__Mastermind 28560 points

    Unfortunately 2700 MHz is a current hole in our VCO frequencies.

    • One method is to use an external VCO on CLKin1.
      • It is possible to use LMX2582 VCO as external VCO with LMK0482x by locking the LMX2582, then tri-stating the LMX2582 charge pump and then activating the LMK0482x charge pump.
    • Another option could be to use an LMX2582 or LMX2541 to provide the 2700 MHz clock.  Two ways to do this...
      • Reference to LMX, the LMX drives converter and CLKin1 of LMK0482x (LMK0482x acts as distribution device)
      • Reference to LMK, the LMK drives the LMX reference.

    Does the 2.7 GHz clock require a JESD204B sysref pulse?  With what accuracy must you provide it?  +/- n device clock cycle allowance?

    73,
    Timothy