An integration-type high speed analog-to-digital converter

An analog-to-digital converter consisting of a switched-capacitor integrator, comparator, and control circuit is presented. The conversion process consists of voltage-to-frequency conversion to determine the upper M bits of an N-bit representation of an input analog voltage and subsequent voltage-to-time conversion to determine the remaining lower N-M bits. The total clock cycle required for N-bit resolution is 2^M+2^N-M at most. The circuits for the two conversions have most of their components in common and thus can be implemented with minimum component count. Error analysis shows that a conversion accuracy higher than 12 bits can be expected from a CMOS monolithic realization. Prototype converters built using discrete components have confirmed the principles of operation