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LMK04808: LKM04808 configuration problem

Sunny Qin
Expert 4890 points
Part Number: LMK04808

Hi team,

one of my customer meet some problem on LMK04808 configuration:

they want output 6 and output 7 of LMK04808 come from the first stage VCO, and the divider of output 6 and output 7 is 2, but they find the power on configuration will failed some time(the confituration started several seconds after power on), especially in low temperature condition, this will happened every time, but all the other output is right, and both two VCO are locked.

when they configure output 6 and output 7 from the second VCO after power on, and then make a second configuration to change to first VCO, then this failure become much better, but still happens some time.

so do you have some comments on this issue, or do you have some suggestion on configure output 6 and output 7 from the first VCO.

Thanks very much.

Regards, Sunny.

  • 0
    TI__Mastermind 28550 points

    Hello Sunny,

    On power up, the default register configuration would result in CLKout6 as LVCMOS (Norm/Norm) and CLKout7 as power down, with CLKout6/7 being driven from the first VCO (CLKout6_7_OSCin_Sel = 0x01, OSCin port).  The CLKout6_7_DIV = 1.  Does this output reliably occur?

    Sunny Qin said:
    they find the power on configuration will failed some time(the confituration started several seconds after power on), especially in low temperature condition, this will happened every time, but all the other output is right, and both two VCO are locked.


    When you say power on configuration, I think you are referring to the first programming after power-up?  And in this programming customer programs.

    • CLKout6 and 7 = to what Clock Output Format?
    • CLKout6_7_DIV = 2.
    • CLKout6_7_OSCin_Sel = 1, OSCin port.

    Sunny Qin said:
    they want output 6 and output 7 of LMK04808 come from the first stage VCO, and the divider of output 6 and output 7 is 2, but they find the power on configuration will failed some time(the confituration started several seconds after power on), especially in low temperature condition, this will happened every time, but all the other output is right, and both two VCO are locked.

    What is the failure?

    What is the low temperature tested at?

    73,
    Timothy