Improved Charge-shared Match-line Sensing Scheme for Dynamic Energy Reduction in TCAM

Abstract

ABSTRACTTernary content addressable memory (TCAM) is used for high-speed table look-up. A match-line (ML) sensing scheme to reduce energy consumption in ML during look-up is presented. The look-up is performed in two steps. In the first step, small segment of each TCAM word is compared with the search key to detect most of the mismatched words. These words remain deactivated in the next step causing energy saving. In the second step, the charge stored in a matched ML first segment is recycled by allowing charge sharing with second ML segment. Charge recycling and absence of ML charging from power supply make total energy consumption low. Post-layout simulation of the scheme implemented using 180 nm 1.8 V CMOS logic shows that for a search time of 2479 ps, the scheme can provide larger noise margin than some popular techniques. It offers at least 80%, 31%, and 29% energy savings compared to the conventional, current-race, and state of the art charge sharing scheme, respectively. For 32 nm technology node, the energy savings are at least 46% and 15% compared to the current-race and the existing charge sharing scheme, respectively.