A ratio-independent algorithmic analog-to-digital converter combining current mode and dynamic techniques

An algorithmic analog-to-digital converter (ADC) that combines current mode and dynamic techniques is presented. The converter does not rely on high-gain amplifiers or well-matched components to achieve high resolution and is inherently insensitive to the amplifier´s offset voltage. An analysis of the converter´s limitations indicates that the resolution of practical circuits will be limited by the switch-induced charge injection. Ultimately, however, the kT/C noise leads to an area/resolution tradeoff and the transistor´s thermal noise leads to a speed/power tradeoff. A prototype fabricated using a 3-μm CMOS process achieved 10-bit resolution at a sampling rate of 25 kHz on an area of only 0.18 mm²