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CDCM6208V2EVM: Incorrect Output frequency

Shadi El morsy
Prodigy 40 points

Part Number: CDCM6208V2EVM

Dear TI,

I am viewing the output of the EVM on a Spectrum analyser. Using the Default hardware setup and GUI.
The desired output and measured output do not match. The measured output is about +22 to +25 MHz greater than the desired output.

So outputting 200 MHz i see 245 MHz on the Spectrum analyser. 

I have attached some images and the Settings.ini.

I can't seem to figure out what is going wrong.

Kind Regards,

Shadi

Register 0: 01B9
Register 1: 0000
Register 2: 001D
Register 3: 08F4
Register 4: 30EC
Register 5: 0000
Register 6: 0000
Register 7: 0022
Register 8: 0002
Register 9: 0000
Register 10: 0000
Register 11: 0000
Register 12: 0000
Register 13: 0000
Register 14: 0000
Register 15: 0000
Register 16: 0000
Register 17: 0000
Register 18: 0000
Register 19: 0000
Register 20: 0000
Register 21: 0001
Register 40: 000A
Inputs:
Primary Input Frequency: 25
Secondary Input Frequency: 25
Version 2
C1: 0
R2: 0
C2: 0
R3: 0
C3: 0
Charge Pump: 0

  • 0
    TI__Expert 5325 points

    Hello Shadi,
    it seems like you still have a default EVM with CDCM6208V2. We ship this EVM with a 30.72 MHz crystal on SEC_REF input.

    With your config it will try to go for 3.68 GHz VCO frequency which roughly translates to the 245 MHz which you are measuring.

    Update the feedback divider from 30 to 25 (press calibrate button in the GUI after doing this).
    This way the device should be able to calibrate and lock the PLL. Your output will then be 204.8 MHz.

    Either you will have to re-work the crystal to a 25 MHz or 50 MHz model. Then you can go for 3GHz VCO frequency. Or you have a signal generator or arbitrary signal generator around. Then you can feed 25 MHz to PRI_REF SMA and continue from there. (If you should not have this available, you can supply 3.3V to VDD_PRI and VDD_SEC. Then use the 10 MHz LVTTL reference from the spectrum analyzer and use that on PRI_REF input. --> feedback of 75)
     
    Please let me know when that helped.

    Best regards,
    Patrick