A reconfigurable 5-to-14 bit SAR ADC for battery-powered medical instrumentation

In battery-powered medical instrumentation, the resolution and signal bandwidth of analog-to-digital converters (ADCs) have to be adapted to the needs of the application to avoid power wastage. This paper presents a reconfigurable successive approximation register (SAR) ADC implemented in 130 nm CMOS that resolves 5-14 bit with a maximum achievable effective number of bits (ENOB) of 13.5 using non-subtractive dither. In the proposed ADC design, the power consumption can be traded for accuracy to improve the energy efficiency and extend its application range, while reducing system integration complexity. A figure-of-merit (FoM) of 59 fJ/conversion is achieved at 1.2 V supply and the converter occupies an area of 0.42mm2. Measurement results of the ADC integrated in a multi-channel analog front-end (AFE) circuit show the suitability of the ADC for portable medical monitoring devices.