Power Efficient Design of Zero-Crossing-Based Switched-Capacitor Circuits

The zero-crossing-based integrator (ZCBI) is an attractive low-power alternative to the conventional switched-capacitor integrators that are based on operational transconductance amplifiers. The zero-crossing detector (ZCD) and the current source in a ZCBI controls the charge transfer with much less static power consumption. However., the ZCBI requires the reset phase where the integrator output is reset to 0 V and this may increase the dynamic power consumption. This paper presents a couple of circuit techniques to reduce the dynamic power consumption and increase the speed/accuracy of ZCBIs. The proposed techniques have been applied to a second-order Delta-Sigma ADC and it achieves the 68.8-dB peak SNR for the bandwidth of 0.39 MHz with the power consumption of $\mathbf{286}\mu\mathbf{W}$ from a 1.2-V power supply.