LOW POWER CONTENT ADDRESSABLE MEMORY ARCHITECTURE

摘要

A low power CAM architecture is disclosed. Matchlines of the CAM array are segmented into a pre search portion and a main search portion. After issuing a search command, a pre search operation is conducted on the pre search portion of the matchline. If the result of the pre search is a match, then the main search is subsequently conducted on the main search portion of the matchline. If the result of pre search is a mismatch, then the main-search is disabled, and consequently there is no power dissipation on the main search portion of the matchlines. Pre search and main search operations can be pipelined to maintain high throughput with minimum latency. Power consumption is further reduced by using a matchline sense circuit for detecting a current on the pre search and main search portions of the matchline. Matchlines are decoupled from the sense circuit sense node in order to achieve higher sensing speed and improved sense margins, and dummy matchlines are used to generate timed control signals for latching the output of the matchline sense circuits. The matchlines are initially precharged to a miss condition represented by ground potential and are then undergo accelerated precharge to a preset voltage potential level below VDD to overcome tail-out parasitic current and to minimize the voltage swing of the matchlines to conserve power.