To drastically reduce the power dissipation of absolute difference accumulators (ADA) for MPEG-4 motion estimation (ME), two types of ADAs (carry-select-type and counter-type) and a fast ME algorithm called an "improved breaking-off-search (IBOS)" algorithm were developed. The carry-select-type ADA and the counter-type ADA have not only small circuit volumes, but also short critical-pass lengths so that power dissipation of ADAs were greatly reduced. IBOS allowed using gated-clock pulses that was able to stop inactive circuits resulting in saving power dissipation. A two-stage pipeline was also incorporated so critical-pass lengths, consequently, supply voltages were reduced resulting in further power reduction. A power of 0.13-μm CMOS counter-type ADA was reduced to 51.8μW, which was about 1/6 that of an equivalent conventional ADA and about 1/51 that of the previously developed 0.13-μm CMOS Wallace-tree ME circuit. A self-controllable-voltage-level (SVL) circuit that was able to drastically reduce stand-by leakage power of CMOS logic circuits has also been developed. The stand-by power of the counter-type ADA incorporating the SVL circuit was 9.43 nW, 9.11 of that of an equivalent ripple carry adder-type ADA.
展开▼
