Testing the performance of delta-sigma ADCs

Available test techniques and their suitability for testing delta-sigma analog-to-digital converters (ADCs) are reviewed. Two commonly-used dynamic tests, sine-wave curve fitting and discrete finite Fourier transform analysis, are discussed in some detail. It is noted that conventional ADC performance measures such as peak error and integral and differential nonlinearity are not readily applicable to delta-sigma ADCs that employ feedback and oversampling. The sinusoidal minimum-error test method for delta-sigma ADCs, described by B.E. Boser (1988), which is based on spectral estimation techniques, is reviewed. With this method, the error at the output of a converter is determined by minimizing the power of the difference between the output signal and a template comprising a sinusoid at the frequency of the input signal, a DC offset, and explicitly evaluated harmonics. The method is compared with sine wave fitting.<
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