A Virtual-ADC Digital Background Calibration Technique for Multistage A/D Conversion

A nonlinear adaptive digital calibration technique for multistage analog-to-digital converters (ADCs) is presented. The approach is derived from a replica-path scaling principle inspired by the parallel-ADC equalization architecture. The treatment of residue gain nonlinearities leads to potentially significant power savings for a simple modification of the first ADC stage. The design tradeoffs involved in this technique, particularly a band-limited interpolator employed, are discussed in detail. Computer simulations demonstrate signal-to-noise-plus-distortion-ratio and spurious-free-dynamic-range improvements from 40 to 90 dB and 45 to more than 100 dB, respectively, for a 15-bit pipelined ADC.