An Energy-Efficient All-Digital Time-Domain-Based CMOS Temperature Sensor for SoC Thermal Management

We propose an all-digital on-chip time-domain temperature sensor for system-on-a-chip (SoC) thermal management. For on-chip purposes, the proposed temperature sensor achieves energy- and area-efficient and fast thermal monitoring by adopting a digitally controlled oscillator (DCO) with the frequency divider and XNOR gate to generate temperature-dependent pulse. The frequency divider with the fine delay unit allows DCO of the proposed structure to have a smaller number of delay cells than a conventional open-loop delay line while maintaining resolution. The use of DCO with frequency divider, which consists of three flip-flops, reduced the required delay line length by 16 times. XNOR gate facilitates the fast thermal monitoring by simply providing the temperature-proportional pulse without additional processing. Temperature measurement results are provided with a digital code generated by a simple counter-based time-to-digital conversion. The proposed temperature sensor is fabricated using 0.13-μm CMOS technology and achieves a low-energy consumption of 2.3 nJ at a conversion rate of 293 kHz with a resolution of 0.72 °C and an area of 0.036 mm². The proposed sensor also obtains a measurement error of -2.4 °C to 2.16 °C from nine test chips over a temperature range of 20 °C-120 °C, which is suitable for SoC thermal management.