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CDCM6208: Crystal Input of CDCM6208

Lacey Lin
Intellectual 2900 points
Part Number: CDCM6208

Hi team,

My customer use the Crystal input for the CDCM6208. The part number is the 8Z25000019(TXC). below is the input schematic.

Can you help to comment below questions:

1. For the Crystal input, customer find they can't drive the CDCM6208 to output the correct frequency when the temperature is high. please help to look at if the input network is suitable for the CDCM6208.

2. For the Crystal input of CDCM6208, what's the main requirement for the specs of the Crystal?

3. Customer also try to add an adjustable resistor in the Pin3 of crystal to measure the negative resistance, but no matter the R2020 is 510ohm or 0 ohm, the negative resistance tested are all 120ohm. Does it make sense?

Thanks a lot!

Lacey

  • 0
    TI__Expert 4400 points
    (1) Are you saying that the output frequency is off by some ppm" at higher temperature? Or does the device not provide an output at hot temperature? What is the value of the series resistor?
    (2) Please look at table 6.11 of CDCM6208 datasheet for specs on the crystal.
    (3) Negative resistance can be measured by adding series resistance to the point of not seeing an oscillation. What is the value that customer added before they stop seeing the oscillation?