Full-Speed Testing of A/D Converters

High-precision analog-to-digital converters (ADC’S) are sought for digital audio and instrumentation and high-speed converters for video applications. Improved methods of converter testing at full speed are needed. This paper describes improved computer-aided ADC characterization methods based on the code density test and spectraf analysis using the fast Fourier transform (FFT). The code density test produces a histogram of the digital output codes of an ADC sampling a known input. The code density can be interpreted to compute the differential and integral nonlinearities, gain error, offset error, and internal noise. Conversion-rate and frequency-dependent behavior can also be measured.