A novel approach to calibrate open-loop amplifier nonlinearities through piecewise linear interpolation

A new digitally assisted background calibration method, applying piecewise linear interpolation instead of ROM and LUT, is presented. The method aims to correct the linear and nonlinear errors introduced by the inter-stage open-loop amplifier. Data approach is adopted to achieve third order error compensation, without applying of ROM and LUT. The calibration algorithm is verified in a 12 bits 40MHz pipeline ADC, the ADC is simulated under Global Foundry 0.18um CMOS technology. Simulation results show that, the algorithm converges in 500 samples. By applying the calibration, the DNL improves 0.25LSB, INL improves 18LSB, SFDR changes from 36.1dB to 78.8dB.