A switched capacitor subranging A/D conversion technique

A capacitor ratio independent subranging analog-to-digital (A/D) conversion technique is proposed. Conversion is performed by using high resolution coarse and fine reference voltage levels. The digital-to-analog (D/A) converter in the structure generates coarse and fine reference voltage levels for subranging A/D conversion. These reference voltages are stored in a capacitor array which is refreshed periodically. High-resolution A/D conversion is achieved by comparing the input voltage with these voltage levels. The proposed subranging A/D conversion technique also uses a parallel structure for analog subtraction. Improved resolution is obtained without increasing the number of conversion steps. Simulation of the algorithm in PSPICE shows results that are consistent with theoretical analysis