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CDCE72010 / CDC7005 apllication questions

John Monforte
Prodigy 20 points
Other Parts Discussed in Thread: CDCE72010, CDCM7005

I want to clean external clocks that are very low frequency (about 50KHz), then mutiply them 256x to tweak a VCXO. It is not clear in the specs that the 72010 and 7005 will function at such a low frequency. Will they work in that range? Also, I need to multiply the external input, but the datasheets describe the "m" coefficient as a divider. Still an application note for the 7005 shows an application that does multiply. How does it accomplish that?

I hope this description is sufficient, but I am standing by to clarify if that is necessary!

  • 0
    TI__Intellectual 1600 points

    Hi John,

    Thanks for your email.

    The 50kHz input frequency is not a problem and both parts can work at that frequency. I recomend you not using AC coupling for the input, DC coupling is better for that input frequency.

    The CDCE72010 and the CDCM7005 have external VCXO. That means that if you want to multiply by 50 then you need an external VCXO of 12.8MHz (256 x 50kHz). That's the way you get higher frequencies. The advantage will be that the jitter of the output will be very low compared to the input (jitter cleaning function).

    Please let us know if you have further question regarding this parts.

     

    Regards,

    Justo