A micropower low-voltage multiplier with reduced spurious switching

We describe a micropower 16times16-bit multiplier (18.8 muW/MHz @1.1 V) for low-voltage power-critical low speed (les5 MHz) applications including hearing aids. We achieve the micropower operation by substantially reducing (by ~62% and ~79% compared to conventional 16times16-bit and 32times32-bit designs respectively) the spurious switching in the Adder Block in the multiplier. The approach taken is to use latches to synchronize the inputs to the adders in the Adder Block in a predetermined chronological sequence. The hardware penalty of the latches is small because the latches are integrated (as opposed to external latches) into the adder, termed the latch adder (LA). By means of the LAs and timing, the number of switchings (spurious and that for computation) is reduced from ~5.6 and ~10 per adder in the adder block in conventional 16times16-bit and 32times32-bit designs respectively to ~2 in our designs. Based on simulations and measurements on prototype ICs (0.35 mum three metal dual poly CMOS process), we show that our 16times16-bit design dissipates ~32% less power, is ~20% slower but has ~20% better energy-delay-product (EDP) than conventional 16times16-bit multipliers. Our 32times32-bit design is estimated to dissipate ~53% less power, ~29% slower but is ~39% better EDP than the conventional general multiplier