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Clarification on simultaneous usage of both the VCO's of CDCE62005 device

Vinay57187
Prodigy 50 points
Other Parts Discussed in Thread: CDCE62005

I intend to configure the registers in the CDCE62005 device to generate 76.8MHz clock (with auxillary being connected to 38.4MHz crystal) and also get a synthesized 40MHz AND 80MHz outputs (from 80MHz oscillator connected to the primary).

As it is, I'm using one internal VCO for generating 76.8MHz (LVDS) and using 80MHz oscillator, i'm deriving 80MHz (LVDS) and 40MHz (LVDS) outputs.

I wanted to know if other frequencies like 66MHz or so on can be derived simultaneously by using another VCO. 

 

Request help!!!

 

Vinay

  • 0
    TI__Expert 4150 points

    Hello Vinay,

    I am not fully clear of your intentions. The CDCE62005 only has one internal VCO. Therefore you can only synthesize integer down-divides of the internal VCO on the outputs, or you can switch an output into bypass mode and use the primary or secondary input directly to drive the ouput divider (as you plan to do with the 80MHz). If you desire 76.8MHz on the output from the internal VCO, the VCO itself will run at 1843.2MHz. In such case, you can not get 66MHz from the same VCO, as it's not an integer down divide. You could however supply 66MHz to the SEC reference in addition to 80MHz to PRI reference. Just make sure you don't enable the smart mux, but select AUX in only.

    The latest CDCE62005 GUI has a feature that allows you to check if a certain frequency is actually possible to be achieved. This tool also considers the bypass mode for certain outputs. It does not consider to give the device more than one frequency on the 3 inputs (but as you already discovered this is possible). To install the latest GUI, go here:

    http://e2e.ti.com/support/clocks/m/videos__files/224554.aspx

     

     

    best regards, Fritz

  • 0 in reply to Fritz
    Prodigy 50 points

    Hello Fritz,

    Thanks for the help. This was a strong reinforcement for my thought.

    Best Regards, Vinay