An untrimmed 12-bit fork-free capacitive analog-to-digital converter

摘要

An M-bit all-capacitive analog-to-digital (A/D) converter (10) which includes 2N switched capacitors (CP01-CP16 and CN01-CN16) of substantially identical capacitance for use in determining the N most significant bits. Each of the capacitors have one terminal connected to a common node (19) and its other terminal switchable to either ground or a positive reference voltage (V¿R?). At the beginning of a conversion cycle, the common node (19) is at a potential indicative of a sampled analog input voltage (Va), a first group of 2?N-1¿ capacitors (20) are switched to ground, and a second group of 2N-1 capacitors (30) are switched to the positive reference voltage (V¿R?). For a given conversion cycle, selected capacitors of one of the capacitor groups are sequentially switched to drive the common node (19) voltage to ground. A method is also disclosed for converting analog signals to digital signals utilizing parallel capacitive elements of substantially identical capacitance.