Ultra-Low Power Data Converters with BEOL NEM Relays

Abstract

With the fundamental limitation on transistor scaling and energy efficiency, Nano-electromechanical (NEM) relays have emerged as a promising alternative solution for ultralow power integrated circuits due to their zero leakage and steep subthreshold properties. In this paper, we explore the implementation of the I/O interface circuits, namely the analog-todigital converter (ADC) and the digital-to-analog converter (DAC), with back-end-of-line (BEOL) NEM relays. The proposed design for the ADC comparators eliminates the need for reference generation by utilizing a bank of NEM relays with different pullin voltages. The decoder and encoder of both data converters are optimized by using a minimum number of devices and exclusive, non-leaking paths for each input and output code. As a result, while the sampling rate and operation frequency of the relaybased converters are inherently lower than CMOS counterparts due to mechanical nature of operation, the proposed data converters can achieve at least one order of magnitude lower energy consumption, which makes them appealing alternatives for ultra-low power VLSI and Internet of Things (IoT) applications.

MEM Relay For the Internet of Things Applications

“…In this way, the previous front-end-of-line area does not need to spare any for the relay circuits. An example of a BEOL relay can be found in [24]. With the usage of metal and VIA (vertical interconnect access) layers, we designed a miniaturized BEOL relay that has a much smaller pull-in voltage (around 2 V) and shorter tM (less than 20 ns), pointing out the feasibility of MHz operation.…”

A Compact Low-Power Mem Resonator-Based Analog to Digital Converter With Feedthrough Signal Cancellation

“…Multiple MEMS-based DACs have been illustrated using relays [2], resonators [3,4], electrostatic actuators [5], and bent-beam electro-thermal actuators [6]. MEMS-based ADCs, on the other hand, are generally more difficult to implement.…”

“…The piezoelectric ADC produces a thermometer code at the output which requires additional circuits to obtain the final binary bits. A NEM relay-based ADC was presented in [2], in which a thermometer code is produced at the output using a bank of relays, designed to have different pull-in voltages. A relay-based decoder design was also proposed to obtain the final binary number.…”

BEOL NEM Relay-Based Inductorless DC-DC Converters

“…In addition, by constructing the relay vertically, it dramatically reduces the device footprint, which is another crucial factor in integrated circuits. As a result, unique pass-relay logic and its circuit applications were studied in [13], relay data converter circuits for input/output interface were proposed in [14], and relay memory cell arrays were reported in [15].…”