I'm using an AD9648 to capture the output data of a single-end analog output circuit. And the captured data is analysed by FPGA. During testing, I found as follows:
- Sampling under 55MHz/fin=5MHz sinwave, output spectral of ADC has no spur
- Sampling over 55MHz/fin=5MHz sinwave, output noise floor is normal while the spur is arising. And some spur is bigger than harmonic.
- Sampling over 55MHz without fin, output noise floor is normal and no spur is found in output spectral
According to the datasheet of AD9648, the spur should not so big.
Any help you can provide would be appreciated!