A scheme for wide input range precision SAR ADC

This paper presents a new scheme for enabling wide input voltage range for SAR (successive approximation register) ADCs. Precision ADC usually favors large input voltage range (>3V), while a push for higher throughput often calls for the use of low voltage devices in fine lithography. There are elegant solutions to bridge the gap. Recently a new type of SAR ADCs using passive charge sharing technique or reservoir capacitor techniques emerges. Previous solutions of dealing with large input range are not compatible with this newly developed SAR ADCs. This paper presents a new scheme to make a wide input voltage range possible for this type of ADCs. Simulation results confirmed it is an appealing and elegant solution. This scheme is not very exciting for traditional SAR ADCs. But it is the only elegant solution for the passive charge sharing ADC as the author now knows.