An autoranging switched-capacitor analog-to digital converter

A novel switched-capacitor serial analog-to-digital (A/D) converter is developed based on the dual-slope integration. The analog voltage being converted is first accumulated into the capacitor in the form of charge. The quantized reference charge is then extracted from the accumulated signal charge until the voltage across the capacitor becomes zero. To increase the resolution, the autoranging function is incorporated which changes the charge accumulation count in 2's geometric progression manner according to the input analog voltage. The resultant counts in charge accumulation and extraction give the exponent and the mantissa, respectively, of the floating-point binary representation. A resolution of 10 bits with the additional $2{1 \over 2}$ bits for the exponent is achieved by the prototype converter built using discrete components.