A 6.4 nW 1.7% Relative Inaccuracy CMOS Temperature Sensor Utilizing Sub-Thermal Drain Voltage Stabilization and Frequency-Locked Loop

Abstract

A 6.4 nW 1.7 % relative inaccuracy (R-IA) CMOS subthermal drain voltage-based temperature sensor is proposed. The proposed stabilized sub-thermal drain voltage current generator achieves a highly linear PTAT output without nonlinearity fitting or postfabrication trimming, and increases the accuracy of the sensor. A combination of the current generator and a frequency-locked-loop relaxes the tradeoff between power and temperature stability of the current-tofrequency converter, and achieves supply-voltage-independent operation. Measured results of the prototype fabricated in a 65 nm CMOS process show that the proposed temperature sensor has a-1.0/+0.7 °C inaccuracy (= R-IA of 1.7 %) while achieving a resolution of 75 mK over a temperature range of-30 to 70 °C. The line sensitivity of the sensor is 2.8 °C/V.

A 0.6V–1.8V Compact Temperature Sensor With 0.24 °C Resolution, ±1.4 °C Inaccuracy and 1.06nJ per Conversion

“…The circuits reported in [8], [15], [16], [19] do not support operation with sub 1 V voltages, while sensors discussed in [9], [14]- [16] show poor voltage scalability. On the contrary, our sensor supports the larger supply voltage operating range from 0.6 V to 1.8 V, while exhibiting a supply sensitivity of about 8 °C/ V. In addition, it does not require any external reference signal unlike the circuits reported in [25] and [26], which use a reference clock [26] and a reference voltage [25], respectively. Moreover, the proposed design exhibits a relatively small footprint of just 0.021 mm 2 .…”

“…Table I summarizes measurement results of the temperature sensor as compared to alternative CMOS designs [8]- [11], [13]- [16], [19], [25], [26]. Experimental results provided for our design come from measurements on 20 test chips, while that of most of the competitors are based on a smaller number of samples (except for [8] and [26]).…”

Fully-Integrated Timers for Ultra-Low-Power Internet-of-Things Nodes—Fundamentals and Design Techniques

“…17, we can observe that the closed-loopbased timer in general achieves a better TC with the same energy efficiency. Despite fewer components in an openloop based timer, the comparators consume the majority of power to safeguard the TC of the timer, which leads to extra power usage and deteriorates the energy efficiency [59]. Contrarily, even the close-loop-based timer entails more components, the comparator and the logic gates have minimal impact on the frequency of the timer.…”

An all-digital CMOS temperature sensor with a wide supply voltage range

“…With the rapid development of the Internet of Things (IoT) recently [1], temperature sensors are increasingly widely being employed in on-chip power thermal management of SoCs and high-performance microprocessors. Since cooling technologies have not kept pace with the increasing energy densities of modern processes, currently.…”

“…Since cooling technologies have not kept pace with the increasing energy densities of modern processes, currently. Overheating will significantly damage system performance, such as accelerated aging, lowering dependability, and even leading to system failure [1]. Therefore, dozens of smart temperature sensors are strategically placed near both hot and cold pots to monitor the system's real-time temperature.…”