Ultralow power voltage reference circuit for implantable devices in standard CMOS technology

Abstract

An ultralow power CMOS voltage reference for body implantable devices is presented in this paper. The circuit core consists of only regular threshold voltage PMOS transistors, thus leading to a very reduced output voltage dispersion, defined as ∕ , and extremely low power consumption. A mathematical model of the generated reference voltage was obtained by solving circuit equations, and its numerical solution has been validated by extensive electrical simulations using a commercial circuit simulator. The proposed solution incorporates a passive RC low-pass filter, to enhance power supply rejection (PSR) over a wide frequency range, and a speed-up section, to accelerate the switching-on of the circuit. The prototype was implemented in 0.18 m standard CMOS technology and is able to operate with supply voltages ranging from 0.7 to 1.8 V providing a measured output voltage value of 584.2 mV at the target temperature of 36 • C. The measured ∕ dispersion of the reference voltage generated is 0.65% without the need of trimming. At the minimum supply of 0.7 V, the experimental power consumption is 64.5 pW, while the measured PSR is kept below -60 dB from DC up to the MHz frequency range. KEYWORDS design methodology, picowatt, subthreshold, trim-free, ultralow power, voltage reference Int J Circ Theor Appl. 2019;47:991-1005.wileyonlinelibrary.com/journal/cta

pMOS‐only pW‐power voltage reference with sub‐10 ppm/°C trimmed temperature coefficient and sub‐100 ppm/V line sensitivity

“…Using the same type of transistors leads to smaller output voltage variations. In addition, compared to Dong et al and Pereira-Rial et al, 21,22 two types of transistors (thick and thin oxide) are used to produce the desired output voltage with fewer transistors. The body effect is removed from M 3 , which decreases V TH3 and increases V REG1 .…”