Using Switched-RC Integrators

Low-voltage, low-power and medium-accuracy analog-to-digital converters (ADCs) are essential components in portable devices. Low-voltage operation of these ADCs poses three major challenges. First, the floating switches required in conventional switched-capacitor implementations are not operational for very low supply voltages. Second, reduced supply voltage translates to reduced signal power, mandating lower noise circuits. Third, the rail-to-rail input required to maximize signal power introduces added distortion in both the switches (due to signal-dependent ON resistance and charge injection) and amplifiers (due to limited output swing). Hence, low-voltage operation generally results in excessive power dissipation, and often requires voltage boosting [1] and/or bootstrapping [2]. In this paper, architectural and circuit techniques are proposed to overcome these problems, and a 0.6V 1mW delta-sigma audio ADC employing these techniques is presented.