A Continuous-Time ADC/DSP/DAC System With No Clock and With Activity-Dependent Power Dissipation

A continuous-time system that converts its analog input to a continuous-time digital representation without sampling, then processes the information digitally without the aid of a clock, is presented. Without sampling there is no aliasing, which reduces the in-band distortion power by not aliasing into band out-of-band distortion components. The 8-bit system, fabricated in a 90 nm CMOS process, utilizes continuous delay elements as part of a programmable transversal FIR filter. The input is encoded by a delta modulator without a clock into a series of non-uniformly spaced tokens, which are processed by the digital continuous-time filter and converted to an analog output using a custom DAC that guarantees there are no glitches in the output waveform. All activity is signal driven, automatically affording dynamic power scaling that tracks input activity.