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CDCE925

Jean Paul Luong
Prodigy 10 points
Other Parts Discussed in Thread: CDCE925

Hello,

 

I would like to use the CDCE925 to program 2 outputs frequency: 74.17MHz and 148.35MHz from 54MHz input frequency.

The Pdiv is 10 bit (from 1 to 1024) and the FVco is limited between 80 MHz to 230MHz.

If I want to set 148.35MHz output, I have to set M=1; N=2750 and Pdiv=1001 (Fout=(Fin/Pdiv)x (N/M)=(54MHz /1001) x (2750/1)=148.35MHz).

However FVco=Fin x (N/M)= 54MHZ x 2750=148 500 MHz wich exceed 230MHz. What happen if the FVco is exceeded 230MHz?

What do you advise.? Is the chip able to provide this output frequency?

Many thanks,   Jean Paul

  • 0
    TI__Expert 5725 points

    Jean Paul,

    It is not recomended to program the vco to a frequency above the value specified in the datasheet.

    There is a sw that would help you to find the setup for CDCE925 given an input and output frequency. 

    http://www.ti.com/litv/zip/scac119

    By using that sw it will generate the setup that would provide out of a 1.8V LVCMOS input of 54MHz  a 3.3VLVCMOS output of 74.17MHz and another 3.3 LVCMOS output of 148.35MHz.

     

     

    Please find attached the setup file in intel hex format and in text format.