ESTIMATION OF AVERAGE ENERGY BASED ON AVERAGE LENGTH CARRY CHAINS CONSUMPTION OF RIPPLE-CARRY ADDER

We show theoretically that the average energy consumption of a ripple-carry adder is O(W), and the upper bound on the average energy consumption is O(W log2 W), where W is the word-length of the operands. Our theoretical analysis is based on a simple state transition diagram (STD) model of a full adder cell and the observations that the average length of a carry propagation chain is v = 2, and the average length of the maximum carry chain is v 5 logzW. To verify our theoretical conclusions, we use the HEAT CAD tool to estimate the average power consumed by the ripple-carry adder for word-lengths 4 5 W 5 64. The experimental results show that, for W 2 16, the error in our theoretical estimations is around 15%.

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