A Resistor-Based Time-Domain CMOS Temperature Sensor With +0.9 °C/−0.9 °C Inaccuracy (3σ) From −40 °C to 125 °C

As the functionality of system-on-chip (SoC) devices continues to increase, the issue of chip heating becomes more severe. Real-time temperature detection with on-chip temperature sensors for effective thermal management has become increasingly important. This article presents a CMOS temperature-to-digital converter based on resistor ratios. It converts temperature to frequency by two relaxation oscillators (ROSCs) of identical structure, utilizing resistors with different temperature coefficients, thereby quantizing the temperature in the time domain. It effectively integrates the advantages of resistor sensing and time-domain quantization, including high accuracy, high flexibility, high compaction, and low-power noise sensitivity. The prototype was fabricated using a 130-nm BCD process, occupying a compact area of 0.025 mm2. It achieves a resolution of 86 mK and an inaccuracy (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$3\sigma $ </tex-math></inline-formula>) of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\pm 0.9~^{\circ }$ </tex-math></inline-formula> C following two-point calibration across the temperature range of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$- 40~^{\circ }$ </tex-math></inline-formula> C to 125 ° C. The supply sensitivity remains below 4 ° C/V for voltage levels ranging from 1.3 to 1.6 V. The temperature sensor works without external reference voltage or clock, features a conversion time of 0.12 ms, and consumes <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$169~\mu $ </tex-math></inline-formula> W at 25 ° C. It is particularly suitable for applications in SoC.