Chen Chun-Chi, Chen Chao-Lieh, Lin Yi
Department of Electronic Engineering, National Kaohsiung First University of Science and Technology, Kaohsiung 81146, Taiwan.
Sensors (Basel). 2016 Jan 30;16(2):176. doi: 10.3390/s16020176.
This paper proposes the first all-digital on-chip linearity enhancement technique for improving the accuracy of the time-domain complementary metal-oxide semiconductor (CMOS) smart temperature sensor. To facilitate on-chip application and intellectual property reuse, an all-digital time-domain smart temperature sensor was implemented using 90 nm Field Programmable Gate Arrays (FPGAs). Although the inverter-based temperature sensor has a smaller circuit area and lower complexity, two-point calibration must be used to achieve an acceptable inaccuracy. With the help of a calibration circuit, the influence of process variations was reduced greatly for one-point calibration support, reducing the test costs and time. However, the sensor response still exhibited a large curvature, which substantially affected the accuracy of the sensor. Thus, an on-chip linearity-enhanced circuit is proposed to linearize the curve and achieve a new linearity-enhanced output. The sensor was implemented on eight different Xilinx FPGA using 118 slices per sensor in each FPGA to demonstrate the benefits of the linearization. Compared with the unlinearized version, the maximal inaccuracy of the linearized version decreased from 5 °C to 2.5 °C after one-point calibration in a range of -20 °C to 100 °C. The sensor consumed 95 μW using 1 kSa/s. The proposed linearity enhancement technique significantly improves temperature sensing accuracy, avoiding costly curvature compensation while it is fully synthesizable for future Very Large Scale Integration (VLSI) system.
本文提出了首个用于提高时域互补金属氧化物半导体（CMOS）智能温度传感器精度的全数字片上线性度增强技术。为便于片上应用和知识产权复用，采用90纳米现场可编程门阵列（FPGA）实现了全数字时域智能温度传感器。尽管基于反相器的温度传感器具有较小的电路面积和较低的复杂度，但必须使用两点校准才能实现可接受的误差。在校准电路的帮助下，单点校准支持极大地降低了工艺变化的影响，减少了测试成本和时间。然而，传感器响应仍表现出较大的曲率，这严重影响了传感器的精度。因此，提出了一种片上线性度增强电路来使曲线线性化并实现新的线性度增强输出。该传感器在八个不同的赛灵思FPGA上实现，每个FPGA中的每个传感器使用118个切片，以展示线性化的优势。与未线性化版本相比，在-20°C至100°C范围内进行单点校准后，线性化版本的最大误差从5°C降至2.5°C。该传感器在1kSa/s时功耗为95μW。所提出的线性度增强技术显著提高了温度传感精度，避免了成本高昂的曲率补偿，同时它可完全综合用于未来的超大规模集成电路（VLSI）系统。
