A 1.1 V 25 ppm/°C Relaxation Oscillator with 0.045%/V Line Sensitivity for Low Power Applications

Abstract

A fully-integrated CMOS relaxation oscillator, realized in 40 nm CMOS technology, is presented. The oscillator includes a stable two-transistor based voltage reference without an operational amplifier, a simple current reference employing the temperature-compensated composite resistor, and the approximated complementary to absolute temperature (CTAT) delay-based comparators compensate for the approximated proportional to absolute temperature (PTAT) delay arising from the leakage currents in the switches. This relaxation oscillator is designed to output a square wave with a frequency of 64 kHz in a duty cycle of 50% at a 1.1 V supply. The simulation results demonstrated that the circuit can generate a square wave, with stable frequency, against temperature and supply variation, while exhibiting low current consumption. For the temperature range from −20 °C to 80 °C at a 1.1 V supply, the oscillator’ output frequency achieved a temperature coefficient (T.C.) of 12.4 ppm/°C in a typical corner in one sample simulation. For a 200-sample Monte Carlo simulation, the obtained T.C. is 25 ppm/°C. Under typical corners and room temperatures, the simulated line sensitivity is 0.045%/V with the supply from 1.1 V to 1.6 V, and the dynamic current consumption is 552 nA. A better figure-of-merit (FoM), which equals 0.129%, is displayed when compared to the representative prior-art works.

A 2.5-nA Area-Efficient Temperature-Independent 176-/82-ppm/$^\circ$C CMOS-Only Current Reference in 0.11-$\mu$m Bulk and 22-nm FD-SOI

“…i.e., a PTAT voltage with a CWT offset as shown in Fig. 3(a), with which solving (5) gives an inversion level i f 2 that decreases with temperature [Fig. 3(b)].…”

“…Moreover, sensor nodes must be able to operate in a wide range of deployment scenarios. The sensitivity of current references to process, voltage and temperature (PVT) variations should therefore be mitigated, as it can profoundly undermine the performance of common analog building blocks such as real-time clock generators [4], [5], temperature sensors [6], [7], and capacitive sensor interfaces [8]. Finally, silicon area must be limited to reduce the production cost and direct environmental footprint of each sensor, especially given the expected massive production volume of the IoT [9].…”

Ultra-Low-Power ICs for the Internet of Things

“…Sinusoidal oscillators based on second-generation voltage conveyors are investigated in [11], while a relaxation oscillator with valuable line sensitivity for Low Power Applications is shown in [12].…”