Digital Circuit Design for Minimum Transient Energy and a Linear Programming Method

This paper provides a theoretical basis for eliminating or reducing the energy consumption due to transients in a synchronous digital circuit The transient energy is minimized when every gate has no more than one output transition per clock cycle This condition is achieved for a gate when the gate delay equals or exceeds the maxi mum di erence between path delays at gate inputs In practice path delays are adjusted either by increasing gate delays or by inserting delay bu ers The mini mum transient energy design is obtained when no delay bu er is added This design requires possible increases in gate delays to meet the minimum energy condition at all gates However the delay of the critical path may be in creased In an alternative design where the critical path delay is not allowed to increase delay bu ers may have to be added The theory in this paper allows trade o s be tween minimum transient energy and critical path delay We formulate the problem as a linear program to obtain the minimum transient energy design with the smallest number of delay bu ers for a given overall delay of the circuit An optimized four bit ALU circuit is found to consume peak and average power compared to the original circuit