Comparative Analysis of Universal Shift Register with and without Clock Gating in VLSI Design

Y. Sowmya, K. Suganthi, Vijayakumar Ponnusamy

 Department of ECE, College of Engineering & Technology, SRM Institute of Science and Technology, Kattankulathur,  Chennai -India-603203

sy8190@srmist.edu.in

suganthk@srmist.edu.in

 vijayakp@srmist.edu.in

DOI: 10.46793/BISEC25.429S

ABSTRACT: One essential component of contemporary VLSI circuit design is effective power management. A popular method for reducing dynamic power usage is clock gating, which selectively disables the clock signal to registers that are not in use. In this study, two variants of a 4-bit Universal Shift Register (USR) written in Verilog HDL – one with and one without clock gating – are com-pared in detail. Using a 32nm CMOS technology library and Synopsys Design Compiler, the design is synthesized and examined to determine how it affects important performance parame-ters including area, power consumption, gate count, and timing. The results show that clock gat-ing substantially minimizes extravagant clock switching and dynamic power dissipation while introducing additional logic overhead, resulting in increased area and gate count. Clock gating improves power efficiency, but implementing it into practice might present problems like com-plex synthesis limitations, propagation delays, and glitches. For the purpose of evaluating these trade-offs across a variety of design factors, a thorough comparative analysis is carried out. a 4-bit Universal Shift Register (USR) with and without clock gating is compared using a 32nm CMOS technology. Clock gating reduces sequential power by 4.05% while increasing area by 16.54% (67.12 µm² to 78.22 µm²) and leaky power by 27.38%. It enhances timing with a 6.67% decrease in critical path delay (0.30 ns to 0.28 ns), even if the overall dynamic power increases by 6.78%. These findings demonstrate the trade-offs of clock gating, which makes it an essential method for designing VLSIs with low power consumption. The findings shed light on the prac-ticality of clock gating in sequential circuits, most significantly for shift registers, and serve as a framework for designers looking to optimize low-power VLSI designs while balancing power, area, and performance requirements.

KEYWORDS: Clock Gating, Universal Shift Register, Low-Power VLSI, Verilog, Synopsys

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