CDCE925: The adjustment range using the VCXO is too small

Hi

 Several questions need to be confirmed:

1. Can only CL be changed by register? C1 C0 is the parameter of crystal oscillator and PCB itself, which cannot be changed by software

2. Whether the value of C1 C0 must be marked by the crystal oscillator datasheet, or it must be determined according to the actual PCB situation

3. CL can be adjusted up to 20PF, what if the range is not enough?Whether an external capacitor is required

4. The following is my schematic diagram, TI clock pro configuration and crystal oscillator datasheet, help guide how to adjust

Hello,

1. Correct, only CL can be changed by the software

2. Some datasheets include the C1 and C0 values. Can you check the datasheet of your xtal?

3. For CL > 20 pF, use additional external capacitors. Also, the value of the device input capacitance has to be considered which always adds 1.5 pF (6 pF/2 pF) to the selected CL.

4. In your schematic, C12 and C13 have a value of 270 with no units. What are the units for those capacitors?

Thanks,

Cris