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CDCM7005 basic questions

Sara Caron76
Prodigy 150 points
Other Parts Discussed in Thread: CDCM7005

I have some basic questions about the CDCM7005:

a) If unused do the YnA and YnB outputs need to be terminated with 150 ohms?

b) I am using the jitter cleaner to lock a 1.2 GHz sine wave VCO. What power  level does the sine wave have to be for the CDCM7005 to lock it? Does it need a balun and if so, what is the impedance of the VCXO_P AND VCXO_N?

 

  • 0
    TI__Expert 3520 points

    Hi Sara,

    a) If outputs are unused, it's highly recommended that you trun them off (tri-state) using the corresponding control bits (Word1- bits 7-26), see datasheet page 19,23

    In that case you don't need terminate. if you didn't turn them off, power consumption will unnecessarily increase and you might experience undesired coupling from floating outputs.

    b) According to recommended operating conditions, Vinpp (Vvcxo_in - Vvcxo_inb) of 500mV min,  (D/S, page 6) However, device would work with lower input levels with some noise performance impact as reduced slew rate at the input mihgt increase output jitter.

    - Typical value of single ended input capacitance of VCXO_P/N is 1.5pF. (D/S, page 9)

    Regarding your question about the balun: I assume you want to use a single-ended VC(X)O, The answe is no, you don't need to use a balun. rather, you need to terminate the other input properly, and take into account that the input now sees only single-ended levels.

    for more details about how to connect the single-ended VCXO, please check this application report

    Kind Regards,

    Ahmed