Skip to main content
eScholarship
Open Access Publications from the University of California

Scalable digital CMOS comparator using a parallel prefix tree

  • Author(s): Abdel-Hafeez, S
  • Gordon-Ross, A
  • Parhami, B
  • et al.
Abstract

We present a new comparator design featuring wide-range and high-speed operation using only conventional digital CMOS cells. Our comparator exploits a novel scalable parallel prefix structure that leverages the comparison outcome of the most significant bit, proceeding bitwise toward the least significant bit only when the compared bits are equal. This method reduces dynamic power dissipation by eliminating unnecessary transitions in a parallel prefix structure that generates the N-bit comparison result after [log4N]+[log16N]4 CMOS gate delays. Our comparator is composed of locally interconnected CMOS gates with a maximum fan-in and fan-out of five and four, respectively, independent of the comparator bitwidth. The main advantages of our design are high speed and power efficiency, maintained over a wide range. Additionally, our design uses a regular reconfigurable VLSI topology, which allows analytical derivation of the input-output delay as a function of bitwidth. HSPICE simulation for a 64-b comparator shows a worst case input-output delay of 0.86 ns and a maximum power dissipation of 7.7 mW using 0.15-μ TSMC technology at 1 GHz. © 2012 IEEE.

Many UC-authored scholarly publications are freely available on this site because of the UC Academic Senate's Open Access Policy. Let us know how this access is important for you.

Main Content
Current View