Review Article
Recent Subthreshold Design Techniques
Table 1
Comparison of effect of different techniques for further power-performance improvements.
| Criteria | References | [9] | [10] | [11] | [12] |
| Technique | ABB | balancing by BB | Frequency scaling | ABB and sizing | Technology | 0.13 μm | 65 nm | 0.13 μm | 0.13 μm | Circuit | FIR Filter | JPEG coprocessor | General-purpose sensor processor | 8-bit processor | Frequency | 98 KHz at 280 mV 240 Hz at 85 mV | 2.5 MHz at 400 mV | 833 KHz at 200 mV | 77–354 KHz | Performance Impact | 2.6x faster at 200 mV 1.25x faster at 1.2 V | Delay improvement from 14 ns to 10 ns | 1.09x faster due to library selection | 3.6x improvement at 300 mV | Energy/Power Impact | 40 nW at 85 mV | 0.75 pJ per cycle at 400 mV 1.0 pJ per cycle at 450 mV | 2.6 pJ/instruction at 360 mV | 3.5 pJ/inst at 350 mV at 354 KHz 515 fJ/inst at 290 mV at 77 KHz | Min voltage (mV) | 85 [13] | 350 | 200 | 140 (24% reduction to zero BB) | Min energy voltage (mV) | 85 | 350 | 360 | 350 (total) 290 (core) | Pros | Mismatch prevention | Mismatch prevention, fast | Frequency optimisation | Preventing PT variations, sizing | Cons | Temp variations not addressed | Not energy conservative, VT variations not addressed | Temp variations and mismatches were not fully investigated | A complicated off-chip BB system |
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