Increasing the ADC precision with oversampling in a flash ADC

Abstract

This paper proposes new design to implement high resolution ADC using the idea of oversampling in flash ADCs. We used 6-bit Flash ADC with 65 times oversampling to gain a resolution of 12-bit Flash ADC. Conventional Flash ADCs are implemented using 2n comparators while proposed design requires only (26 + L(n)) comparators, Where L(n) is an exponential operator in n with order less than 2n/3. This reduction in chip area would reduce power consumption, since sampling rates for both (conventional Flash ADC and proposed) designs are the same. Signal-to-Noise ratio (SNR) and Distortion (SINAD) of the proposed 12-bit Oversampled-Flash ADC output was only at most 1.7% decrease compared to ideal 12-Bit Sigma-Delta (∑Δ) ADC. Moreover if an ideal 6-bit flash ADC is used to implement a 12-bit Oversampled-Flash ADC, DNL and INL values for proposed 12-bit oversampled-Flash ADC would be zero.