abstract: Space exploration is a large field that requires high performing circuitry due to the harsh environment. Within a space environment one of the biggest factors leading to circuit failure is radiation. Circuits must be robust enough to continue operation after being exposed to the high doses of radiation. Bandgap reference (BGR) circuits are designed to be voltage references that stay stable across a wide range of supply voltages and temperatures. A bandgap reference is a piece of a large circuit that supplies critical elements of the large circuit with a constant voltage. When used in a space environment with large amounts of radiation a BGR needs to maintain its output voltage to enable the rest of the circuit to operate under proper conditions. Since a BGR is not a standalone circuit it is difficult and expensive to test if a BGR is maintaining its reference voltage. This thesis describes a methodology of isolating and simulating bandgap references. Both NPN and PNP bandgap references are simulated over a variety of radiation doses and dose rates. This methodology will allow the degradation due to radiation of a BGR to be modeled easily and affordably. It can be observed that many circuits experience enhanced low dose rate sensitivity (ELDRS) which can lead to failure at low total ionizing doses (TID) of radiation. A compact model library demonstrating degradation of transistors at both high and low dose rates (HDR and LDR) will be used to show bandgap references reliability. Specifically, two bandgap references being utilized in commercial off the shelf low dropout regulators (LDO) will be evaluated. The LDOs are reverse engineered in a simulation program with integrated circuit emphasis (SPICE). Within the two LDOs the bandgaps will be the points of interest. Of the LDOs one has a positive regulated voltage and one has a negative regulated voltage. This requires an NPN and a PNP based BGR respectively. This simulation methodology will draw conclusions about the above bandgap references, and how they operate under radiation at different doses and dose rates. / Dissertation/Thesis / Masters Thesis Electrical Engineering 2019

<p>This thesis investigates the possibility of realizing bandgap reference crcuits for processes having sub-1V supply voltage. With the scaling of gate oxide thickness supply voltage is getting reduced. But the threshold voltage of transistors is not getting scaled at the same rate as that of the supply voltage. This makes it difficult to incorporate conventional designs of bandgap reference circuits to processeshaving near to 1V supply voltage. In the first part of the thesis a comprehensive study on existing low voltage bandgap reference circuits is done. Using these ideas a low-power, low-voltage bandgap reference circuit is designed in the second part of the thesis work. </p><p>The proposed bandgap reference circuit is capable of generating a reference voltage of 0.730V. The circuit is implemented in 0.18µm standard CMOS technology and operates with 0.9V supply voltage, consuming 5µA current. The circuit achieves 7 ppm/K of temperature coefficient with supply voltage range from 0.9 to 1.5V and temperature range from 0 to 60C.</p>

This thesis investigates the possibility of realizing bandgap reference crcuits for processes having sub-1V supply voltage. With the scaling of gate oxide thickness supply voltage is getting reduced. But the threshold voltage of transistors is not getting scaled at the same rate as that of the supply voltage. This makes it difficult to incorporate conventional designs of bandgap reference circuits to processeshaving near to 1V supply voltage. In the first part of the thesis a comprehensive study on existing low voltage bandgap reference circuits is done. Using these ideas a low-power, low-voltage bandgap reference circuit is designed in the second part of the thesis work. The proposed bandgap reference circuit is capable of generating a reference voltage of 0.730V. The circuit is implemented in 0.18µm standard CMOS technology and operates with 0.9V supply voltage, consuming 5µA current. The circuit achieves 7 ppm/K of temperature coefficient with supply voltage range from 0.9 to 1.5V and temperature range from 0 to 60C.

This work deals with principles of design low noise bandgap reference using multiple in the process EPI92. The voltage reference is described and theoretic analysis noise performances is made. Results are compared with measured data realized breadboard BG reference and fabricated low drop-out regulators, which using different accurate bandgap references cells.

<p>Many analog systems need a stable power supply voltage that does not vary with temperature and time in order to operate properly. In a battery operated system the battery voltage is not stable, e.g. it decreases with decreasing temperature and with ageing. In that case a voltage regulator must be used, that regulates the battery voltage and generates a stable supply voltage to power other circuitry. </p><p>In this thesis a voltage regulator to be used in a battery operated system has been designed which meets the given specification of stability and power capabilities. A voltage reference, which is a commonly used devise in analog circuits, was also designed. The role of a reference voltage in an electrical system is the same as for a tuning fork in a musical ensemble; to set a standard to which other voltages are compared. </p><p>A functionality to detect when the lifetime of the battery is about to run out was also developed.</p>

Many analog systems need a stable power supply voltage that does not vary with temperature and time in order to operate properly. In a battery operated system the battery voltage is not stable, e.g. it decreases with decreasing temperature and with ageing. In that case a voltage regulator must be used, that regulates the battery voltage and generates a stable supply voltage to power other circuitry. In this thesis a voltage regulator to be used in a battery operated system has been designed which meets the given specification of stability and power capabilities. A voltage reference, which is a commonly used devise in analog circuits, was also designed. The role of a reference voltage in an electrical system is the same as for a tuning fork in a musical ensemble; to set a standard to which other voltages are compared. A functionality to detect when the lifetime of the battery is about to run out was also developed.

Bandgap reference circuits are used in a host of analog, digital, and mixed-signal systems to establish an accurate voltage reference for the entire IC. The most used CMOS implementation for voltage references is the bandgap circuit due to its high predictability, and low dependence of the supply voltage and temperature of operation. This work studies a CMOS implementation of a resistor-less bandgap reference, which consumes low power. The most relevant and traditional approaches usually employed to implement bandgap voltage references are investigated. The impact of process, power-supply, load and temperature variations has been analyzed and simulated. The functionality of critical components of the circuit has been verified through chip implementation. / text

As the technology advances, the feature size of the modern integrated circuits (ICs) has decreased dramatically to nanometer amplitude. On one hand, the shrink brings benefits, such as high speed and low power consumption per transistor. On the other hand, it poses a threat to the reliable operation of the ICs by the increased radiation sensitivity, such as single event effects (SEEs). For example, in 2010, a commercial-off-the-shelf (COTS) BiCMOS DC/DC pulse width modulator (PWM) IC was observed to be sensitive to neutrons on terrestrial real-time applications, where negative 6-μs glitches were induced by the single event transient (SET) effects. As a result, a project was set up to comprehensively study the failure mechanisms with various test methodologies and to develop SET-tolerant circuits to mitigate the SET sensitivity. First, the pulsed laser technique is adopted to perform the investigation on the SET response of the DC/DC PWM chip. A Ti:Sapphire single photon absorption (SPA) laser with different wavelengths and repetition rates is used as an irradiation source in this study. The sensitive devices in the chip are found to be the bandgap voltage reference circuit thanks to the well-controlled location information of the pulsed laser. The result is verified by comparing with the previous alpha particle and neutron testing data as well as circuit simulation using EDA tools. The root cause for the sensitivity is also acquired by analyzing the circuit. The temperature is also varied to study the effect of the temperature-induced quiescent point shift on the SET sensitivity of the chip. The experimental results show that the quiescent point shifts have different impacts on SET sensitivities due to the different structures and positions of the circuitries. After that, heavy ions, protons, and the pulsed X-ray are used as irradiation sources to further study the SET response of the DC/DC chip. The heavy ion and pulsed laser data are correlated to each other. And the equivalent LETs for laser with wavelengths of 750 nm, 800 nm, 850 nm and 920 nm are acquired. This conclusion can be used to obtain the equivalent heavy ion cross section of any area in a chip by using the pulsed laser technique, which will facilitate the SET testing procedure dramatically. The proton and heavy ion data are also correlated to each other based on a rectangular parallel piped (RPP) model, which gives convenience in Soft Error Rate (SER) estimation. The potential application of pulsed X-ray technique in SET field is also investigated. It is capable of generating similar results with those of heavy ion and pulsed laser testing. Both the advantages and disadvantages of this technique are explained. This provides an alternative choice for the SET testing in the future. Finally, the bandgap voltage reference circuit in the DC/DC PWM is redesigned and fabricated in bulk CMOS 130nm technology and a SET hardened bandgap circuit is proposed and investigated. The CMOS substrate PNP transistor is much less sensitive to SETs than the BiCMOS NPN transistor according to the pulsed laser test results. The reason is analyzed to be the different fabrication processes of the two technologies. The laser test results also indicate that the SET hardened bandgap circuit can mitigate the SET amplitude dramatically, which is consistent with the SPICE simulation results. These researches provide more understandings on the design of SET hardened bandgap voltage reference circuit.

Using bandgap engineering, silicon-germanium (SiGe) BiCMOS technology effectively combines III-V transistor performance with the cost and integration advantages associated with CMOS manufacturing. The suitability of SiGe technology for cryogenic and radiation-intense environments is well known, yet SiGe has been generally overlooked for applications involving extreme high temperature operation. This work is an investigation into the potential capabilities of SiGe technology for operation up to 300°C, including the development of packaging and testing procedures to enable the necessary measurements. At the device level, SiGe heterojunction bipolar transistors (HBTs), field-effect transistors (FETs), and resistors are verified to maintain acceptable functionality across the temperature range, laying the foundation for high temperature circuit design. This work also includes the characterization of existing bandgap references circuits, redesign for high temperature operation, validation, and further optimization recommendations. In addition, the performance of temperature sensor, operational amplifier, and output buffer circuits under extreme high temperature conditions is presented. To the author's knowledge, this work represents the first demonstration of functional circuits from a SiGe technology platform in ambient temperatures up to 300°C; furthermore, the optimized bandgap reference presented in this work is believed to show the best performance recorded across a 500°C range in a bulk-silicon technology platform.

Silicon carbide (SiC) integrated circuits (ICs) can enable the emergence of robust and reliable systems, including data acquisition and on-site control for extreme environments with high temperature and high radiation such as deep earth drilling, space and aviation, electric and hybrid vehicles, and combustion engines. In particular, SiC ICs provide significant benefit by reducing power dissipation and leakage current at temperatures above 300 °C compared to the Si counterpart. In fact, Si-based ICs have a limited maximum operating temperature which is around 300 °C for silicon on insulator (SOI). Owing to its superior material properties such as wide bandgap, three times larger than Silicon, and low intrinsic carrier concentration, SiC is an excellent candidate for high-temperature applications. In this thesis, analog and mixed-signal circuits have been implemented using SiC bipolar technology, including bandgap references, amplifiers, a master-slave comparator, an 8-bit R-2R ladder-based digital-to-analog converter (DAC), a 4-bit flash analog-to-digital converter (ADC), and a 10-bit successive-approximation-register (SAR) ADC. Spice models were developed at binned temperature points from room temperature to 500 °C, to simulate and predict the circuits’ behavior with temperature variation. The high-temperature performance of the fabricated chips has been investigated and verified over a wide temperature range from 25 °C to 500 °C. A stable gain of 39 dB was measured in the temperature range from 25 °C up to 500 °C for the inverting operational amplifier with ideal closed-loop gain of 40 dB. Although the circuit design in an immature SiC bipolar technology is challenging due to the low current gain of the transistors and lack of complete AC models, various circuit techniques have been applied to mitigate these problems. This thesis details the challenges faced and methods employed for device modeling, integrated circuit design, layout implementation and finally performance verification using on-wafer characterization of the fabricated SiC ICs over a wide temperature range. / <p>QC 20170905</p>