[FAQ] ADC Noise: How is ADC noise measured and specified?

There are two methods ADC manufacturers use to measure ADC noise. The first method shorts the ADC’s inputs together to measure the slight variations in output code as a result of thermal noise. The second method involves inputting a sine wave with a specific amplitude and frequency (such as 1 V_PP at 1 kHz) and reporting how the ADC quantizes the sine wave. Figure 2 demonstrates these types of noise measurements.

Figure 2: Sine-wave-input test setup (left) and input-short test setup (right)

Which ADCs use which type of measurement method? Read more about noise measurement methods and specifications in part 2.