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LMH1983: No input when turning on the power supply

KAEDE KUDO
Expert 2700 points

Part Number: LMH1983

Hello,

I have a Question about LMH1983.

[Q]

My customer use LMH1983 with no input when turning on the power supply.
In that case, should I set the LMH1983 below?

1) LOR MODE = Free Run, when turning on the power supply.
2) After Input is OK, LOR MODE = Holdover Mode 

Or is it OK to set Holdover from the beginning?

I am concerned about how Holdover Mode works with no input from the beginning. (How is the output of VC_LPF?)

Best Regards,

Kaede Kudo

  • 0
    TI__Mastermind 32575 points
    I suggest to configure Free-run on LOR mode after power-up if you want to establish a stable constant VC_LPF voltage at mid-rail (or other voltage, as configured by VC_Free register bits) to give a stable VCXO frequency.

    Alan
  • 0 in reply to Alan O
    Expert 2700 points

    Hello Alan-san,

    Thank you for your fast reply.

    When there was no input at power up, I understood that the output of VC_LPF is indeterminate in Holdover Mode.

    I want to establish a stable frequency after power up with no input.

    So I configure Free-run on LOR mode at power up.

    Best Regards,

    Kaede Kudo