Near-Zero-Power Temperature Sensing via Tunneling Currents Through Complementary Metal-Oxide-Semiconductor Transistors.

Temperature sensors are routinely found in devices used to monitor the environment, the human body, industrial equipment, and beyond. In many such applications, the energy available from batteries or the power available from energy harvesters is extremely limited due to limited available volume, and thus the power consumption of sensing should be minimized in order to maximize operational lifetime. Here we present a new method to transduce and digitize temperature at very low power levels. Specifically, two pA current references are generated via small tunneling-current metal-oxide-semiconductor field effect transistors (MOSFETs) that are independent and proportional to temperature, respectively, which are then used to charge digitally-controllable banks of metal-insulator-metal (MIM) capacitors that, via a discrete-time feedback loop that equalizes charging time, digitize temperature directly. The proposed temperature sensor was integrated into a silicon microchip and occupied 0.15 mm2 of area. Four tested microchips were measured to consume only 113 pW with a resolution of 0.21 °C and an inaccuracy of ±1.65 °C, which represents a 628× reduction in power compared to prior-art without a significant reduction in performance

Doctor of Philosophy

dissertationSince the late 1950s, scientists have been working toward realizing implantable devices that would directly monitor or even control the human body's internal activities. Sophisticated microsystems are used to improve our understanding of internal biological processes in animals and humans. The diversity of biomedical research dictates that microsystems must be developed and customized specifically for each new application. For advanced long-term experiments, a custom designed system-on-chip (SoC) is usually necessary to meet desired specifications. Custom SoCs, however, are often prohibitively expensive, preventing many new ideas from being explored. In this work, we have identified a set of sensors that are frequently used in biomedical research and developed a single-chip integrated microsystem that offers the most commonly used sensor interfaces, high computational power, and which requires minimum external components to operate. Included peripherals can also drive chemical reactions by setting the appropriate voltages or currents across electrodes. The SoC is highly modular and well suited for prototyping in and ex vivo experimental devices. The system runs from a primary or secondary battery that can be recharged via two inductively coupled coils. The SoC includes a 16-bit microprocessor with 32 kB of on chip SRAM. The digital core consumes 350 μW at 10 MHz and is capable of running at frequencies up to 200 MHz. The integrated microsystem has been fabricated in a 65 nm CMOS technology and the silicon has been fully tested. Integrated peripherals include two sigma-delta analog-to-digital converters, two 10-bit digital-to-analog converters, and a sleep mode timer. The system also includes a wireless ultra-wideband (UWB) transmitter. The fullydigital transmitter implementation occupies 68 x 68 μm2 of silicon area, consumes 0.72 μW static power, and achieves an energy efficiency of 19 pJ/pulse at 200 MHz pulse repetition frequency. An investigation of the suitability of the UWB technology for neural recording systems is also presented. Experimental data capturing the UWB signal transmission through an animal head are presented and a statistical model for large-scale signal fading is developed

A programmable microsystem using system-on-chip for real-time biotelemetry

A telemetry microsystem, including multiple sensors, integrated instrumentation and a wireless interface has been implemented. We have employed a methodology akin to that for System-on-Chip microelectronics to design an integrated circuit instrument containing several "intellectual property" blocks that will enable convenient reuse of modules in future projects. The present system was optimized for low-power and included mixed-signal sensor circuits, a programmable digital system, a feedback clock control loop and RF circuits integrated on a 5 mm × 5 mm silicon chip using a 0.6 μm, 3.3 V CMOS process. Undesirable signal coupling between circuit components has been investigated and current injection into sensitive instrumentation nodes was minimized by careful floor-planning. The chip, the sensors, a magnetic induction-based transmitter and two silver oxide cells were packaged into a 36 mm × 12 mm capsule format. A base station was built in order to retrieve the data from the microsystem in real-time. The base station was designed to be adaptive and timing tolerant since the microsystem design was simplified to reduce power consumption and size. The telemetry system was found to have a packet error rate of 10<sup>-</sup><sup>3</sup> using an asynchronous simplex link. Trials in animal carcasses were carried out to show that the transmitter was as effective as a conventional RF device whilst consuming less power

A Programmable CMOS Voltage Controlled Ring Oscillator for Radio-Frequency Diathermy On-chip Circuit

In this work we present the design of a digitally controlled ring type oscillator in 0.5 μm CMOS technology for a low-cost and portable radio-frequency diathermy (RFD) device. The oscillator circuit is composed by a low frequency ring oscillator (LFRO), a voltage controlled ring oscillator (VCRO), and a logic control. The digital circuit generates an input signal for the LFO, which generates a voltage ramp that controls the oscillating output signal of the VCRO in the range of 100 KHz to 1 MHz. Simulation results show that the proposed circuit exhibits controllable output characteristics in the range of 100 KHz – 1 MHz, with low power consumption and low phase noise, making it suitable for a portable RFD device

A Low Power Integrated Circuit for Implantable Biosensor Incorporating an On-Chip FSK Modulator

Medical care has been significantly improved in recent years due to tremendous technological advancement in the field of CMOS technology. Among those improvements, integrated circuit design and sensing techniques have brought to the doctors more flexibility and accuracy of examinations of their patients. For example, a diabetic patient needs to visit a hospital on a regular basis for the examination and proper treatment. However, with the tremendous advancement in electronic technology, a patient can soon monitor his or her own blood glucose level at home or at office with an implantable sensor which can also trigger insulin pump attached to the body. The insulin delivery system can be precisely controlled by the electronics embedded in the implantable device. In this thesis, a low power integrated circuit for the implantable biosensor incorporating an on-chip FSK modulator is presented. This design has been fabricated using AMI 0.5-μm CMOS process available through MOSIS. The simulation and test results are also presented to verify its operation

A Flexible, Highly Integrated, Low Power pH Readout

Medical devices are widely employed in everyday life as wearable and implantable technologies make more and more technological breakthroughs. Implantable biosensors can be implanted into the human body for monitoring of relevant physiological parameters, such as pH value, glucose, lactate, CO2 [carbon dioxide], etc. For these applications the implantable unit needs a whole functional set of blocks such as micro- or nano-sensors, sensor signal processing and data generation units, wireless data transmitters etc., which require a well-designed implantable unit.Microelectronics technology with biosensors has caused more and more interest from both academic and industrial areas. With the advancement of microelectronics and microfabrication, it makes possible to fabricate a complete solution on an integrated chip with miniaturized size and low power consumption.This work presents a monolithic pH measurement system with power conditioning system for supply power derived from harvested energy. The proposed system includes a low-power, high linearity pH readout circuits with wide pH values (0-14) and a power conditioning unit based on low drop-out (LDO) voltage regulator. The readout circuit provides square-wave output with frequency being highly linear corresponding to the input pH values. To overcome the process variations, a simple calibration method is employed in the design which makes the output frequency stay constant over process, supply voltage and temperature variations. The prototype circuit is designed and fabricated in a standard 0.13-μm [micro-meter] CMOS process and shows good linearity to cover the entire pH value range from 0-14 while the voltage regulator provides a stable supply voltage for the system

CMOS ring oscillator delay cell performance: a comparative study

A common voltage-controlled oscillator (VCO) architecture used in the phase locked loop (PLL) is the ring oscillator (RO). RO consist of number of inverters cascaded together as the input of the first stage connected to the output of the last stage. It is important to design the RO to be work at desired frequency depend on application with low power consumption. This paper presents a review the performance evaluation of different delay cell topologies the implemented in the ring oscillator. The various topologies analyzed includes current starved delay cell, differential delay cell and current follower cell. Performance evaluation includes frequency range, frequency stability, phase noise and power consumption had been reviewed and comparison of different topologies has been discussed. It is observed that starved current delay cell have lower power consumption and the different of the frequency range is small as compared to other type of delay cell

A PVT tolerant voltage-controlled oscillator for automotive applications

This thesis focusses on the development of an integrated oscillator for automotive applications. The oscillator operates based on the Barkhausen criterion, which is a mathematical requirement used in electronics to predict whether a linear electronic circuit will oscillate. In this thesis, a voltage-controlled oscillator is designed for increased performance under various process, voltage and temperature (PVT) conditions. By applying a voltage reference block, the output frequency of 0.5MHz, 0.75MHz, 1MHz or 1.25MHz can be obtained. In order to compensate for the variations at PVT corners, the trimming technology is applied to increase the accuracy. The supply voltage is considered to be varying between 2.1V and 5.5V while the temperature range is -40oC -125oC.Includes bibliographical references