LW-DEM: Designing a Low Power Digital-to-Analog Converter Using Lightweight Dynamic Element Matching Technique

Abstract

The need for low-power wireless sensor networks (WSNs) continues to grow. Based on the fact that digital-to-analog converters (DACs) are essential elements in the WSN and consumes a lot of power, this paper presents a new low-power DAC design to realize the low-power WSN. To do that, this paper exploits the dynamic element matching (DEM) technique, one of the well-known techniques for high performance DACs, proposes a lightweight DEM (LW-DEM) technique that minimizes power and area overhead of the DEM technique. More specifically, this paper is motivated from the observation that input data of DACs tends to be sufficiently random that the input data can be used for the random selection of the current source instead of a pseudo-random number generator (PRNG) for the traditional DEM. Because the PRNG consumes a lot of power and occupies a large area in a DAC, elimination of the PRNG from a DAC and utilizing input data result in significant power saving and area reduction in the DAC while meeting the required performance of the low-power WSNs. This paper provides a detailed LW-DEM architecture and its operation principle. To demonstrate the efficacy of the proposed method, a prototype 12-bit DAC using the LW-DEM is implemented. The 12-bit DAC is fabricated in 65 nm CMOS technology and occupies only $0.065~{mm}^{2}$ area. Measurement results with the prototype verify that the DAC using LW-DEM accomplishes 39% power saving and 52% area reduction in the randomizer, compared to a DAC using the conventional DEM. At the same time, the measured spurious-free dynamic range (SFDR) of the DAC using LW-DEM is better than 55 dB, demonstrating that the proposed DAC achieves almost same performance as a DAC using the conventional DEM.