Hello ADI Support Team,
We are currently evaluating the AD9177 DAC and are experiencing issues with its Noise Spectral Density (NSD) performance. Our measurements show a noise floor that is much higher than we expected based on the datasheet.
Problem Details:
Problem Details:
-
Measured NSD: In the DC to 20 MHz frequency range, we are measuring an NSD of approximately -140 dBm.
-
Datasheet Expectation: While the datasheet for the AD9177 doesn't specify an exact NSD value for this low-frequency range, inferring from the performance plots, we would expect it to be significantly better than -164 dBc/Hz. The discrepancy between our measurement and the expected performance is very large.
Our Test Setup:
-
Device: AD9177
-
DAC Mode: JMOD 15C
-
Output Signal: A single-tone signal.
-
Sample Rate (Fs): 12 GSPS
-
Physical Connection: The DAC output is DC-coupled and measured single-endedly directly into a spectrum analyzer.
-
Instrument: Spectrum Analyzer (Our instrument's noise floor is below -150 dBm).
-
Analyzer Settings: RBW is set to 1 Hz.
Our Questions:
-
Is our test methodology—specifically the DC-coupled, single-ended measurement—a valid way to assess the true noise performance of the AD9177?
-
If our test method is flawed, could you please provide or point us to the recommended test procedure for accurately measuring the NSD?
-
Could you also help confirm the expected typical NSD performance (in either dBm/Hz or dBc/Hz) for the AD9177 in the low-frequency band (e.g., DC to 20 MHz)?
Any guidance you could provide would be greatly appreciated.
Thank you.
