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## Über dieses Buch

This book focuses on the design of a Mega-Gray (a standard unit of total ionizing radiation) radiation-tolerant ps-resolution time-to-digital converter (TDC) for a light detection and ranging (LIDAR) system used in a gamma-radiation environment. Several radiation-hardened-by-design (RHBD) techniques are demonstrated throughout the design of the TDC and other circuit techniques to improve the TDC's resolution in a harsh environment are also investigated. Readers can learn from scratch how to design a radiation-tolerant IC. Information regarding radiation effects, radiation-hardened design techniques and measurements are organized in such a way that readers can easily gain a thorough understanding of the topic. Readers will also learn the design theory behind the newly proposed delta-sigma TDC. Readers can quickly acquire knowledge about the design of radiation-hardened bandgap voltage references and low-jitter relaxation oscillators, which are introduced in the content from a designer's perspective.

· Discusses important aspects of radiation-tolerant analog IC design, including realistic applications and radiation effects on ICs;

· Describes a new type of Time-to-Digital (TDC) converter designed for radiation-tolerant application;

· Explains the design and measurement of all functional blocks (e.g., bandgap reference, relaxation oscillator) in the TDC.

## Inhaltsverzeichnis

### 1. Introduction

Abstract
In recent years, the radiation hardness of integrated circuits has drawn more and more attention due to their increasingly important role in electronic systems in space, nuclear, and high-energy particle physics applications. Comprehensive background information regarding this new but rather crucial feature of integrated circuits are discussed in this chapter. Starting with an inspiring story about how integrated circuits pave the way to the Higgs particles, some most interesting potential applications of radiation-hardened electronics are then introduced. It is followed by a detailed explanation of a special implementation, which is the main topic of this book: a radiation-hardened time-to-digital converter for light detection and ranging.
Ying Cao, Paul Leroux, Michiel Steyaert

### 2. Background on Time-to-Digital Converters

Abstract
Time-to-digital converters (TDCs) are key building blocks in time-based mixed-signal systems, used for the digitization of analog signals in time domain. Some commonly used TDC structures are summarized in this chapter. By carefully analyzing their advantages and performance constraints, it has been concluded that in order to design a megagray radiation-tolerant TDC, an innovative and reliable architecture must be developed. More technical details regarding the investigation of this new TDC type will be given in Chap. 4. In order to obtain a fare comparison between the TDC proposed in this book and other state-of-the-art TDCs, performance measures of TDCs are also given in this chapter.
Ying Cao, Paul Leroux, Michiel Steyaert

### 3. Radiation Hardened by Design

Abstract
The major work introduced in this book is to develop a megagray-radiation-tolerant ps-resolution time-to-digital converter (TDC) for a light detection and ranging (LIDAR) application. In this chapter, major radiation effects in complementary metal–oxide–semiconductor (CMOS) integrated circuits (ICs) are introduced. The total ionizing dose (TID) effects are of most concern to this work since they have the largest impact on analog performance of a system. Hierarchical radiation hardened by design (RHBD) strategies are then proposed to improve the radiation tolerance of CMOS devices from four levels: system level, circuit level, device level, and layout level. Finally, the radiation hardness assurance qualification procedure is also given, which has been followed during TID performance evaluation of the demonstrated CMOS ICs presented in this book.
Ying Cao, Paul Leroux, Michiel Steyaert

### 4. Background on Time-to-Digital Converters

Abstract
For the first time, a third-order noise shaping concept has been successfully implemented in the design of time-to-digital converters (TDCs). Two 1-1-1 multistage noise shaping (MASH) $$\Delta\Sigma$$ TDCs are presented in this chapter. Third-order time domain noise shaping has been adopted by the TDCs to achieve better than 6 ps resolution. Following a detailed analysis of the noise generation and propagation in the MASH $$\Delta\Sigma$$ structure, the first prototyping TDC has been realized in 0.13 μm complementary metal–oxide–semiconductor (CMOS) technology. It achieves an effective number of bits (ENOB) of 11 bits and consumes 1.7 mW from a 1.2-V supply. Gamma radiation assessments with both a low dose rate of 1.2 kGy/h and a high dose rate of 30 kGy/h have been performed, proving the TDC’s radiation hardness. In the second MASH TDC, a delay-line-assisted calibration technique is introduced to mitigate the phase skew caused by the large comparator delay, which is the main limiting factor of the MASH TDC’s resolution. The demonstrated TDC achieves an ENOB of 13 bits and a wide input range of 100 ns.
Ying Cao, Paul Leroux, Michiel Steyaert

### 5. Radiation Hardened Bandgap References

Abstract
As a key component in the proposed multistage noise-shaping (MASH) $$\Delta\Sigma$$ time-to-digital converter (TDC) system, the total ionizing dose (TID) radiation tolerance of the bandgap reference in deep-submicron -complementary metal–oxide–semiconductor (CMOS) technology is generally limited by the radiation-introduced leakage current in diodes. An analysis of this phenomenon is given in this book, and a dynamic base leakage compensation (DBLC) technique is proposed to improve the radiation hardness of a bandgap reference built in a standard 0.13 μm CMOS technology. A temperature coefficient (TC) of 15 ppm/°C from -40 to 125 °C is measured before irradiation. The voltage variation from 0 to 100 °C is only ± 1 mV for an output voltage of 600 mV. Gamma irradiation assessment proves that the bandgap reference is tolerant to a total ionizing dose of at least 4.5 MGy. The output reference voltage exhibits a variation of less than 3 $$\%$$ during the entire experiment, when the chip is irradiated by gamma ray at a dose rate of 27 kGy/h.
Ying Cao, Paul Leroux, Michiel Steyaert

### 6. Low-Jitter Relaxation Oscillators

Abstract
The best achievable time resolution of the proposed multistage noise-shaping (MASH) $$\Delta\Sigma$$ time-to-digital converter (TDC) is practically limited by the phase noise performance of the employed relaxation oscillator which generates the quantization clock. After gaining an insight of the noise sources in the relaxation oscillator, a switched-capacitor (SC) integrated error feedback (IEF) technique has been proposed to reduce the closed-in phase noise and improve its clock accuracy. The proposed relaxation oscillator with SC IEF is implemented in 65 nm complementary metal-oxide-semiconductor (CMOS). It demonstrates a phase noise of -101 dBc/Hz at 100 kHz offset frequency, when the center frequency is 12.6 MHz and achieves a figure of merit (FOM) of 152.6 dB. The oscillator occupies an area of 0.01 mm2, and consumes 82 μA from 1.2 V. The frequency changes only ± 0.07% over a supply range of 1.1–1.5 V. From 0 to 80 °C, the total frequency variation is within ± 0.82$$\%$$.
Ying Cao, Paul Leroux, Michiel Steyaert

### 7. Conclusions

Without Abstract
Ying Cao, Paul Leroux, Michiel Steyaert

### Backmatter

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