Proposed time‐mode wide fan‐in NAND and NOR gates

Abstract

Summary CMOS circuits usually operate either in the voltage, current, charge, or time domain. Each of these domains has its own features. As the fan‐in of CMOS circuits increases, the performance of circuits that operate in the voltage domain, the current domain, or the charge domain degrades. This is the case especially with scaling down the power‐supply voltage associated with technology scaling. In this paper, a time‐mode scheme that utilizes a floating‐gate MOSFET (FGMOS) transistor is proposed. The proposed scheme showed good performance for wide fan‐in NAND and NOR gates. The design issues of the proposed scheme like the speed and the power consumption are investigated quantitatively. The performance of the proposed scheme is confirmed through simulation using the 45‐nm CMOS predictive technology model (PTM) with a 1‐V power‐supply voltage. 64‐input NAND and NOR gates realized using this scheme have time delays of 0.375 and 0.25 ns, respectively, at a load capacitance of 5 fF. The application of the proposed scheme for realizing multiplexers required in register files is illustrated and compared with the conventional domino logic in the superthreshold, near‐threshold, and subthreshold regions.