Has the circuit board been checked for shorts, proper pin configurations, short traces, an adequate low-noise ground, etc.?
• Is the reference voltage at the correct value? If an external reference is used, does it have low enough noise? Can it source adequate current? • Is the circuit being tested in a relatively noise-free environment? If not, move to one. Noise tends to find its way into circuits through the power supplies, EMI (electromagnetic interference), lighting, and a host of other sources. • Determine if the noise could be coming from the input-signal source, the analog front-end signal conditioning circuitry, or the ADC itself. Observe the signal source on a spectrum analyzer or an oscilloscope, and examine the output of the front-end circuitry in a similar manner. If an op amp is used on the front-end, make sure that its noise performance is acceptable for the performance desired. • In addition, verify that the ADC has adequate bandwidth at the frequencies of interest. Other things to check are the scope probes, the power supplies for excessive current flow, and the ADC’s programmed state to ma
