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about the cdce62005's registers

Huailong Qi
Prodigy 200 points

hello,

we use a crstal oscillator (25MHz) as the input , and wish to get the following output clocks:

output 0 : 250MHz, LVDS

output 1 : 250MHz, LVDS

output 2 : 250MHz, LVDS

output 3 : 250MHz, LVDS

output 4 : 25MHz, LVDS

 

Are the registers datas right?

reg0:eb840320

reg1:eb840321

reg2:eb840302

reg3:eb840303

reg4: eb1e0314

reg5: 10000be5

reg6:84be03e6

reg7:bd907c27

  • 0
    TI__Expert 4150 points

    Hi,

    your configuration is fine BUT your loop filter is NOT SUFFICIENT. You seem to have a BW of 1.4M (too high) and insufficent phase margin of 25 only.

    Please adjust loop filter components to:
    C1=21.5p

    R2=4k

    C2=473.5pF

    R3=5k

    C3=19.5pF

    CP charge pump current = 600uA

     

    This should get you PM=54, LBW=320k, gamma=0.93

     

    Also, set the smart mux to AUX input only, since you only use XTAL, and disable PRI and SEC input..

    Furthermore, unless you want to us the AUX output at 125MHz, you should disable this output for lowest noise and power consumption.