A Design of Low-Power Bootstrapped CMOS Switch for 20MS/s 12-bit Charge Sharing SAR ADCs

This paper presents the design and implementation of a low-power bootstrapped CMOS switch composed of a 12-bit charge sharing analog-to-digital converter(ADC) for ultrasound diagnostic medical devices. The proposed charge sharing ADC architecture consists of unit capacitor array and switches with low threshold voltage devices to minimize the size of the ADC. As the bootstrapped switch structure is employed, the switch on-resistance is constant regardless of the input voltage swings. It leads to a reduction in the third harmonic distortion caused by on-resistance of the switches. Thus, the proposed ADC with the bootstrapped switches had ENOB of 10.64-bit and SNDR of 65.82dB at the 5MHz input frequency. The designed ADC had the size of 1600um x 505um with 130nm CMOS process.