A 9-Bit Resistor-Based Highly Digital Temperature Sensor With a SAR-Quantization Embedded Differential Low-Pass Filter in 65-nm CMOS With a 2.5-μs Conversion Time

This paper presents a resistor-based area-compact temperature sensor for on-chip thermal detection. It has three unique features: 1) the use of a differential low-pass RC filter (DLPF) for thermal sensing, which reduces the area; 2) successive approximation register (SAR)-quantization embedded in the DLPF, which reuses the DLPF capacitor for capacitive digital-to-analog conversion (CDAC), eliminates the CDAC references, and utilizes the full sensing range for quantization; and 3) a highly digital circuit architecture, which can be easily implemented using a standard digital design flow and migrated to different processes. The temperature sensor was fabricated in a 65-nm CMOS technology occupying 8400-mu m(2) silicon area. It achieves 0.38 degrees C resolution at room temperature. After a two-point calibration, the sensor achieves a 3 sigma inaccuracy of +/- 1.2 degrees C from -30 degrees C to 100 degrees C. It consumes 35.3-mu W power from a 1.1-V supply. With a 2.5-mu s conversion time, the sensor achieves an 88 pi/conversion energy efficiency, which yields a 12.7-pJ.K-2 resolution figure-of-merit (FoM).