Q: Where can I find in the datasheet on how the output of the DDS will drift?
A: The quantitative value on how the output of the DDS will drift is not found in the DDS datasheet.
Frequency drift is an arbitrary offset of a clock source from its nominal frequency. The DDS output is ultimately related to the purity of the clock source used as the system clock of the DDS. That means, if the frequency of the clock source drifts, the output of the DDS will also drift. Thus, the stability of the DDS output depends on how stable the clock source is.
The following table summarizes the best stability each type of oscillator can hold based on today’s manufacturing process:
|
Temperature |
XO |
TCXO |
OCXO |
|
0°C to 70°C |
±10 ppm |
±0.5 ppm |
±0.003 ppm |
|
-20°C to 70°C |
±25 ppm |
±0.5 ppm |
±0.003 ppm |
|
-40°C to 85°C |
±30 ppm |
±1 ppm |
±0.02 ppm |
|
-55°C to 125°C |
±50 ppm |
N/A |
N/A |
For example, if TCXO is used as the clock source (drift is 0.0001% or +/-1ppm), you are likely to see frequency drift in the 1ppm range at the DDS output.
This FAQ was generated from the following discussion: Does the output frequency of a DDS drift?