REDUCTION OF INPUT DEPENDENT CAPACITOR DAC SWITCHING CURRENT IN FLASH-SAR ANALOG-TO-DIGITAL CONVERTERS

Circuits and methods for reducing input dependent capacitor DAC switching current in flash-successive approximation register (SAR) analog-to-digital converters (ADCs) are disclosed. An ADC includes an M-bit flash ADC and N-bit SAR ADC. In flash conversion phase, flash ADC outputs digital signal including most significant M-bits of N-bits of digital output code for a sampled analog signal. SAR ADC includes capacitor DAC and digital engine. The capacitor DAC includes first and second set of capacitors, where first ends of the first and second set of capacitors are coupled to common terminal. The digital engine provides the N-bits of digital output code in SAR conversion phase based on the digital signal and a voltage (Vcom) at the common terminal. During flash conversion phase, second ends of the first set of capacitors are connected to Vref and Vgnd respectively so as to generate a voltage level corresponding to the digital signal as Vcom.