Combating Hot Carrier Effects via Bit-level Transition Balancing

In this paper, we address the issue of hot-carriers and their impact on reducing the reliability of a VLSI circuit by accelerating the aging process of transistors. We tackle this phenomenon by formulating and solving an encoding problem, which we refer to as the Bit-level Transition Balancing (BTB). The BTB problem is to find encoding techniques that minimize the maximum activity over a group of lines, which we refer to as a bus, thus making the whole bus less vulnerable to hot-carrier degradation. We approach this problem systematically by first answering the question of how much information about the characteristics of the data that appears on the bus is needed to find a combinational and/or sequential encoding function that optimally solve the BTB problem. Next, we propose a number of different encoding techniques that efficiently solve the BTB problem. Experimental results demonstrate the effectiveness of such techniques.