A 14.17pJ.K2 FoM CMOS Temperature Sensor With 173 μm2 Sensing Core for Remote Sensing in 65-nm CMOS

This article presents a CMOS transistor-based smart temperature sensor for ON-chip thermal management. The temperature sensor utilizes proportional to absolute temperature (PTAT) and complementary to absolute temperature (CTAT) currents to control their ring oscillators and then generates a digital temperature code accordingly. Replacing a constant with temperature (CWT) current with a CTAT current as the reference brings two benefits: 1) the dynamic range of the output temperature is enlarged and 2) the design complexity of the reference path is reduced. The nonlinearity introduced by the CTAT reference can be mitigated in the circuit design by evaluating its Taylor formula and configuring its parameters. In addition, the proposed design supports both local and remote sensing by placing the paired PTAT and CTAT sensing elements in either a local or remote ON-chip position. Such paired sensing elements’ placement schemes can achieve ultralow area occupation and reduce nonidealities by quantizing the ratio of output frequencies. A prototype sensor occupies
$9148 \mu \text {m}^{{2}}$
with an additional
$173 \mu \text {m}^{{2}}$
for one remote hot-spot sensing in a 65-nm CMOS technology was implemented. After a two-point calibration and system error removal, it achieves
$-0.35\,\,^{\circ }\text{C}$
/+0.58 °C peak-to-peak inaccuracy over 0 °C–95 °C. At the conversion time of 1.2 ms, 0.054 °C resolution is achieved at room temperature. Operating from a 1.0 V supply, it consumes
$4.053 \mu \text{W}$
at room temperature, which yields 14.17 pJ
$\cdot \text {K}^{{2}}$
resolution figure-of-merit (FoM).