Multi-rate Polyphase DSP and LMS Calibration Schemes for Oversampled ADCs

A scaling-friendly approach for the low-power calibration of oversampled analog-to-digital (A/D) systems is presented. A 22-dB amplifier relaxes the design constraints of the analog front-end (AFE). The integrator nonidealities in the AFE of the sigma-delta (ΣΔ) ADC are calibrated using a multi-rate polyphase least-mean squares (LMS) algorithm. The proposed half(fs/2) and quarter-rate (fs/4) LMS calibration schemes reduce computational complexity and achieve more than 2.5× savings in digital power consumption for low-OSR (over-sampling ratio)ΔΣ ADCs, which require higher adaptive filter orders and sampling frequencies. The proposed scheme can have further applications in serial-link I/O and sub-band echo cancellation architectures.