A Continuous-time Adc and Digital Signal Processing System for Smart Dust and Wireless Sensor Applications

In this paper an event-driven (ED) digital signal processing system (DSP), Analog-to-digital converter (ADC) and Digital-to-analog converter (DAC) operating in continuous-time (CT) with smart dust as the target application is presented. The benefits of the CT system compared to its conventional counterpart are lower in-band quantization noise and no requirement of a clock generator and anti-aliasing filter, which makes it suitable for processing burst-type data signals. A clock less EDADC system based on a CT delta modulation (DM) technique is used. The ADC output is digital data, continuous in time, known as “data token”. The ADC used an un buffered, area efficient, segmented resistor string (R-string) feedback DAC. This DAC in component reduction with prior art shown nearly 87.5% reduction of resistors and switches in the DAC and the D flip-flops in the bidirectional shift registers for an 8-bit ADC, utilizing the proposed segmented DAC architecture. The obtained Signal to noise distortion ratio (SNDR) for the 8-bit ADC system is 55.73 dB, with the band of interest as 220 kHz and Effective number of bits (ENOB) of more than 9 bits.