A foreground calibration technique with multi-level dither for a 14-bit 1-MS/s SAR ADC

Abstract

A foreground calibration is proposed to obtain the real weights in the split capacitor digital-to-analog- converter (CDAC) of a 14-bit 1-MS/s successive-approximation-register (SAR) ADC. Since the non-linearity of high-resolution SAR ADC is mainly caused by the mismatch of capacitors, calibration of weights of more significant bits is necessary when the resolution of SAR ADC comes to more than 12 bits. By injecting a multi-level dither signal in both the calibration and conversion phases of the calibration scheme, the precision and non-linearity of SAR ADC can be significantly improved. Simulation results indicate that the peak signal-to-noise-and-distortion ratio (SNDR) and the spurious-free dynamic range (SFDR) achieve 79.93 dB and 91.21 dB by employing the proposed calibration technique in a 14-bit split-CDAC SAR ADC. Besides, integral non-linearity (INL) achieves 0.22 least-significant bit (LSB).