Research On High-performance And Low-cost CMOS Temperature Sensors

CMOS temperature sensors are widely used in various systems on chip,industrial Internet of Things and wireless sensing nodes,due to their small-size,easy-integration,low-cost,and di-rect digital output.However,different applications also bring challenges to CMOS temperature sensor designs.For example,real time clock compensation applications require high-accuracy temperature sensors.On-chip thermal management applications need CMOS temperature sensors to occupy ultra-small areas and to be compatible with a low-supply voltage.In addition,CMOS temperature sensors for IoT applications should have ultra-low power consumptions.It is also im-portant to reduce the calibration cost in mass production.To solve these issues,this thesis consid-ers the requirements of specific applications and develops CMOS temperature sensors according to different signal domains where the temperature is readout.Seven kinds of high-performance and low-cost CMOS temperature sensors are designed and verified.The main contributions and innovations are as follows.1.Research on voltage-domain and current-domain CMOS temperature sensor:(1)the poten-tial multiple stable operating points in the BJT-based analog front-end with current-gain compen-sation are analyzed first and a new low-cost startup circuit is proposed to guarantee the robustness.(2)A new digitally-assisted linearization technique is proposed to meet the requirements of both precision temperature sensing and the compatibility of multi-channel multiplexing in the MCU for energy metering,thereby reducing the cost of system design;(3)With the innovations above and other techniques such as dynamic element matching,finite current gain compensation,and chopper stabilization,a voltage-domain CMOS temperature sensor with versatile readout scheme and high accuracy is designed in a standard 0.13-?m CMOS process.It achieves a measured inaccuracy of±0.47?C(3?)from-40?C to 125?C after one-point calibration.(4)To improve the accuracy of the temperature sensor in an advanced CMOS process,A current-mode readout scheme with dynamic current gain compensation is proposed without any other penalty such as area or power consump-tion;(5)A current-mode temperature sensor is designed and verified in a standard 55-nm CMOS process.It achieves an untrimmed inaccuracy of±1.7?C(3?)from-40?C to 125?C and occupies an area of only 0.0146 mm~2.2.Research on time-domain and frequency-domain CMOS temperature sensors:(1)to over-come the problem that the existing duty-cycle-modulated CMOS temperature sensors usually have large areas and high supply voltages,a new capacitor-reused voltage-to-duty-cycle converter is proposed.Compared to the previous topologies,this architecture can reduce the area of the capac-itor by 50%and improve the accuracy;(2)Using the proposed capacitor-reused voltage-to-duty-cycle converter,two high-performance and low-cost CMOS temperature sensors with duty-cycle-modulated outputs are designed in a standard 0.13-?m CMOS process,one of them is a BJT-based sensor,which can achieve an inaccuracy of±0.38?C(3?)from-10?C to 100?C after one-point cal-ibration,while occupying an area of 0.073 mm~2.The other one is a dynamic-biased resistor-based sensor and it is compatible with a sub-1V supply,while occupying an area of only 0.025 mm~2.(3)Combined the BJT-based analog front-end with a two-Ring Oscillator(RO)-based frequency do-main readout scheme,a temperature sensor with a two-step dynamic-range usage improvement technique is proposed.Fabricated in standard 0.13-?m CMOS process,the sensor can achieve a conversion rate of 75 kSa/s.3.Research on all-digital CMOS temperature sensors:(1)The thesis break the boundary be-tween transitional analog and digital designs.A leakage-based digital CMOS temperature sensor with compact area is proposed.This design has a build-in supply sensitivity suppression mecha-nism,solving the supply sensitivity problem in traditional RO-based readout scheme.(2)A pro-totype sensor,designed and verified in the SMIC 55-nm standard CMOS process,can work with a wide supply voltage range of 0.8 V to 1.3 V while occupying an area of only 1770?m~2.The measured inaccuracy is±0.7?C(3?)from-40?C to 125?C after two-point calibration.(3)Based on the above research,a new delay cell with lower power consumption and more robustness is also proposed and a new versatile FDC with lower power consumption is designed,further improving the performance of the digital temperature sensor.The sensor,verified in the UMC 55-nm CMOS process,maintains a small area(2454?m~2)while achieving lower power consumption(0.86?W)and higher energy efficiency(0.26 pJ·K~2),which is competitive compared with the state-of-the-arts.