Continuous-Time Input Pipeline ADCs

Two continuous-time input pipeline ADC architectures are introduced. The continuous-time input approach overcomes many of the challenges associated with a pure switched-capacitor architecture. The resistive input load of the two new architectures provides a benign interface to external drive circuitry. The switched-capacitor sampling function is moved to the second stage input which greatly eases the sampling distortion requirements and obviates the need for an explicit front-end sample-and-hold function. The second ADC presented additionally provides inherent anti-alias filtering, allowing the possibility of eliminating costly anti-alias filters. This second architecture also eases the jitter requirements of the ADC clock when compared to switched capacitor pipeline ADCs. Measured results obtained from two proof of concept test chips fabricated in a 0.18 mu m CMOS process validate the effectiveness of the proposed techniques.