Current Mode Multipliers and Constant Coefficient Multipliers for Radix N and modulo N Logic Arithmetic

This paper presents new structures of combinatorial and constant coefficient multipliers based on the current-mode gates – digital elements operating with constant, continuous power supply current. Current mode circuits do not perturb the analogue part of the chip integrated on the same die through the parasitic coupling across the substrate with the same strength as voltage mode circuits do. Designed multipliers are intended for use in radix N and modulo N arithmetic units. Proposed structures of multipliers are based on the modulo N current-mode adders, and therefore are simple and regular. Designed constant coefficient multipliers are ROM-based. All these structures were successfully tested in the SPICE simulator. INTRODUCTION The serious problem in the mixed analog-digital systems placed on a common chip surface is the interference between analog and digital parts of the chip. Switching transients in digital circuits can perturb analog circuits integrated on the same die by the parasitic coupling through the substrate [1]. Currentmode gates, proposed by the authors in previous papers [2-6], operate with a continuous, constant current drawn from the power supply, which value practically does not depend on logical states. Therefore, the level of switching transient of digital circuits based on the current-mode gates is essentially lower in comparison with their prototypes based on the classical voltage type of gates. Moreover, current-mode digital circuits (adders, decoders, flip-flops, registers, counters, etc.) need less number of gates in comparison with analog, classical ones (up to 35%) [4, 6]. Note that physical and logical properties of mentioned above currentmode gates differ from corresponding properties of classical voltage-mode gates. Therefore, the authors apply design approaches proposed in [4] to design of current-mode prototypes of digital circuits. For example, paper [4] reports that these approaches were used for design of a current-mode prototype of the Xilinx FPGA’s cell. Generally, digital current-mode circuits operate in multiple-valued logic (MVL) [7]. This feature is useful in design of arithmetic units operating in multiplevalued radix N logic or modulo N arithmetic (adders, ALUs, multipliers, etc.) [8]. Therefore, this paper presents structures of combinatorial MVL and modulo N multipliers, and ROM-based MVL and modulo N constant coefficient multipliers (CCM). All proposed circuits have been successfully tested using the SPICE simulator. CONCEPTION OF ELEMENTARY CURRENT-MODE GATES The conception of the current-mode gate with static noise margins and one of its possible realizations are presented in Fig. 1a and Fig. 1b accordingly.