Abstract
Sensing systems such as biomedical implants, infra- structure monitoring systems, and military surveillance units are constrained to consume only picowatts to nanowatts in standby and active mode, respectively. This tight power budget places ultra-low power demands on all building blocks in the systems. This wo rk proposes a voltage reference for use in such ultra-low power systems, referred to as t he 2T voltage reference, which has been demonstrated in silicon across three CMOS technolo- gies. Prototype chips in 0.13 µm show a temperature coef ficient of 16.9 ppm/°C (best) and line sensitivity of 0.033%/V , while consuming 2.22 pW in 1350 µm². The lowest functional V is 0.5 V. The proposed design improves energy ef ficiency by 2 to 3 orders of magnitude while exhibit ing better line sensitivity and temperature coef ficient in less area, compared to other nanowatt voltage references. For process spread analysis, 49 dies are mea- sured across two runs, showing the design exhibits comparable spreads in TC and output voltage to existing voltage references in the literature. Digital trimming is demonstrated, and assisted one temperature point digital trimming, guided by initial samples with two temperature point trimming, enables TC < 50 ppm/°C and 0.35% output precision across all 25 dies. Ease of technology portability is demonstrated with s ilicon measurement results in 65 nm, 0.13 µm, and 0.18 µm CMOS technologies.