The document explains that while monolithic SAR converters are popular, hybrid or modular units often offer better performance. It details the limitations of standard circuits, specifically DAC settling time and comparator delay, which hinder speed in high-resolution designs.
To overcome these limitations, the text proposes several circuit modifications. These include using a two-speed clock modulation scheme, adding a pre-amplifier stage to increase gain for faster comparison, and implementing closed-loop clock control with active summing node clamping to achieve conversion times as low as 1.8 microseconds.
The basic circuit requires about 12 microseconds to convert.
A simple 12-bit, 12us SAR converter requires about 10us to convert.