A 14-bit 2.5GS/s and 5GS/s RF sampling ADC with background calibration and dither

Abstract

We describe a 14-bit 2.5GS/s non-interleaved pipelined ADC that relies on correlation-based background calibrations to correct the inter-stage gain, settling (dynamic), kick-back and memory errors. A new technique is employed to inject a large dither signal on the input to dither the non-linear kick-back on the ADC driver, and another large dither signal is injected to dither any residual non-linearity in the pipeline. In order to correct the effect of aging on the comparators, a new background calibration technique is employed to correct the comparator offsets. The ADC is fabricated as a dual in a 28nm CMOS process. An optional interleaved mode is provided, where the two ADCs on chip are time-interleaved to obtain a single 14-bit 5GS/s ADC. Background calibration of offset and gain mismatch and fixed calibration of timing mismatch between the two channels are implemented on chip.