Table 1: Comparison of effect of different techniques for further power-performance improvements.

CriteriaReferences
[9][10][11][12]

TechniqueABB 𝑉 t h balancing by BBFrequency scalingABB and 𝑊 + 𝐿 sizing
Technology0.13 μm65 nm0.13 μm0.13 μm
Circuit 8 × 8 FIR FilterJPEG coprocessorGeneral-purpose sensor processor8-bit processor
Frequency98 KHz at 280 mV
240 Hz at 85 mV
2.5 MHz at 400 mV833 KHz at 200 mV77–354 KHz
Performance Impact2.6x faster at 200 mV
1.25x faster at 1.2 V
Delay improvement from 14 ns to 10 ns1.09x faster due to library selection3.6x improvement at 300 mV
Energy/Power Impact40 nW at 85 mV0.75 pJ per cycle at 400 mV
1.0 pJ per cycle at 450 mV
2.6 pJ/instruction at 360 mV3.5 pJ/inst at 350 mV at 354 KHz
515 fJ/inst at 290 mV at 77 KHz
Min voltage (mV)85 [13]350200140 (24% reduction to zero BB)
Min energy voltage (mV)85350360350 (total)
290 (core)
ProsMismatch preventionMismatch prevention, fastFrequency optimisationPreventing PT variations, 𝐿 sizing
ConsTemp variations not addressedNot energy conservative, VT variations not addressedTemp variations and mismatches were not fully investigatedA complicated off-chip BB system