200 research outputs found
Design and Evaluation of Radiation-Hardened Standard Cell Flip-Flops
Use of a standard non-rad-hard digital cell library in the rad-hard design can be a cost-effective solution for space applications. In this paper we demonstrate how a standard non-rad-hard flip-flop, as one of the most vulnerable digital cells, can be converted into a rad-hard flip-flop without modifying its internal structure. We present five variants of a Triple Modular Redundancy (TMR) flip-flop: baseline TMR flip-flop, latch-based TMR flip-flop, True-Single Phase Clock (TSPC) TMR flip-flop, scannable TMR flip-flop and self-correcting TMR flip-flop. For all variants, the multi-bit upsets have been addressed by applying special placement constraints, while the Single Event Transient (SET) mitigation was achieved through the usage of customized SET filters and selection of optimal inverter sizes for the clock and reset trees. The proposed flip-flop variants feature differing performance, thus enabling to choose the optimal solution for every sensitive node in the circuit, according to the predefined design constraints. Several flip-flop designs have been validated on IHPās 130nm BiCMOS process, by irradiation of custom-designed shift registers. It has been shown that the proposed TMR flip-flops are robust to soft errors with a threshold Linear Energy Transfer (LET) from ( 32.4 (MeVā
cm2/mg) ) to ( 62.5 (MeVā
cm2/mg) ), depending on the variant
Single event upset hardened CMOS combinational logic and clock buffer design
A radiation strike on semiconductor device may lead to charge collection, which may manifest as a wrong logic level causing failure. Soft errors or Single Event Upsets (SEU) caused by radiation strikes are one of the main failure modes in a VLSI circuit. Previous work predicts that soft error rate may dominate the failure rate in VLSI circuit compared to all other failure modes put together. The issue of single event upsets (SEU) need to be addressed such that the failure rate of the chips dues to SEU is in the acceptable range. Memory circuits are designed to be error free with the help of error correction codes. Technology scaling is driving up the SEU rate of combinational logic and it is predicted that the soft error rate (SER) of combinational logic may dominate the SER of unpro-tected memory by the year 2011. Hence a robust combinational logic methodology must be designed for SEU hardening. Recent studies have also shown that clock distribution network is becoming increasingly vulnerable to radiation strike due to reduced capaci-tance at the clock leaf node. A strike on clock leaf node may propagate to many flip-flops increasing the system SER considerably. In this thesis we propose a novel method to improve the SER of the circuit by filtering single event upsets in the combinational logic and clock distribution network. Our ap-proach results in minimal circuit overhead and also requires minimal effort by the de-signer to implement the proposed method. In this thesis we focus on preventing the propagation of SEU rather than eliminating the SEU on each sensitive gate
A low power and soft error resilience guard-gated Quartro-based flip-flop in 45 nm CMOS technology
Abstract Conventional flipāflops are more vulnerable to particle strikes in a radiation environment. To overcome this disadvantage, in the literature, many radiationāhardened flipāflops (FFs) based on techniques like triple modular redundancy, dual interlocked cell, Quatro and guardāgated Quatro cell, and so on, are discussed. The flipāflop realized using radiation hardened by design Quatro cell is named as the improved version of Quatro flipāflop (IVQFF). Single event upset (SEU) at inverter stages of master/slave and at output are the two drawbacks of IVQFF. This study proposes a guardāgated Quatro FF (GQFF) using guardāgated Quatro cell and Muller Cāelement. To overcome the SEU at inverter stages of IVQFF, in GQFF, the inverter stages are realized in a parallel fashion. A dualāinput Muller Cāelement is connected to the GQFF output stage to mask the SEU and thus maintain the correct output. The proposed GQFF tolerates both single node upset (SNU) and double node upset (DNU). It also achieves low power. To prove the efficacy, GQFF and the existing FFs are implemented in 45 nm Complementary Metal Oxide Semiconductor (CMOS) technology. From the simulation results, it may be noted that the GQFF is 100% immune to SNUs and 50% immune to DNUs
INVESTIGATING THE EFFECTS OF SINGLE-EVENT UPSETS IN STATIC AND DYNAMIC REGISTERS
Radiation-induced single-event upsets (SEUs) pose a serious threat to the reliability of registers. The existing SEU analyses for static CMOS registers focus on the circuit-level impact and may underestimate the pertinent SEU information provided through node analysis. This thesis proposes SEU node analysis to evaluate the sensitivity of static registers and apply the obtained node information to improve the robustness of the register through selective node hardening (SNH) technique. Unlike previous hardening techniques such as the Triple Modular Redundancy (TMR) and the Dual Interlocked Cell (DICE) latch, the SNH method does not introduce larger area overhead. Moreover, this thesis also explores the impact of SEUs in dynamic flip-flops, which are appealing for the design of high-performance microprocessors. Previous work either uses the approaches for static flip-flops to evaluate SEU effects in dynamic flip-flops or overlook the SEU injected during the precharge phase. In this thesis, possible SEU sensitive nodes in dynamic flip-flops are re-examined and their window of vulnerability (WOV) is extended. Simulation results for SEU analysis in non-hardened dynamic flip-flops reveal that the last 55.3 % of the precharge time and a 100% evaluation time are affected by SEUs
STUDY OF SINGLE-EVENT EFFECTS ON DIGITAL SYSTEMS
Microelectronic devices and systems have been extensively utilized in a variety of radiation
environments, ranging from the low-earth orbit to the ground level. A high-energy particle from
such an environment may cause voltage/current transients, thereby inducing Single Event Effect
(SEE) errors in an Integrated Circuit (IC). Ever since the first SEE error was reported in 1975,
this community has made tremendous progress in investigating the mechanisms of SEE and
exploring radiation tolerant techniques. However, as the IC technology advances, the existing
hardening techniques have been rendered less effective because of the reduced spacing and
charge sharing between devices. The Semiconductor Industry Association (SIA) roadmap has
identified radiation-induced soft errors as the major threat to the reliable operation of electronic
systems in the future. In digital systems, hardening techniques of their core components, such as
latches, logic, and clock network, need to be addressed.
Two single event tolerant latch designs taking advantage of feedback transistors are
presented and evaluated in both single event resilience and overhead. These feedback transistors
are turned OFF in the hold mode, thereby yielding a very large resistance. This, in turn, results in
a larger feedback delay and higher single event tolerance. On the other hand, these extra
transistors are turned ON when the cell is in the write mode. As a result, no significant write
delay is introduced. Both designs demonstrate higher upset threshold and lower cross-section
when compared to the reference cells.
Dynamic logic circuits have intrinsic single event issues in each stage of the operations. The
worst case occurs when the output is evaluated logic high, where the pull-up networks are turned
OFF. In this case, the circuit fails to recover the output by pulling the output up to the supply rail.
A capacitor added to the feedback path increases the node capacitance of the output and the
feedback delay, thereby increasing the single event critical charge. Another differential structure
that has two differential inputs and outputs eliminates single event upset issues at the expense of
an increased number of transistors.
Clock networks in advanced technology nodes may cause significant errors in an IC as the
devices are more sensitive to single event strikes. Clock mesh is a widely used clocking scheme
in a digital system. It was fabricated in a 28nm technology and evaluated through the use of
heavy ions and laser irradiation experiments. Superior resistance to radiation strikes was
demonstrated during these tests.
In addition to mitigating single event issues by using hardened designs, built-in current
sensors can be used to detect single event induced currents in the n-well and, if implemented,
subsequently execute fault correction actions. These sensors were simulated and fabricated in a
28nm CMOS process. Simulation, as well as, experimental results, substantiates the validity of
this sensor design. This manifests itself as an alternative to existing hardening techniques.
In conclusion, this work investigates single event effects in digital systems, especially those
in deep-submicron or advanced technology nodes. New hardened latch, dynamic logic, clock,
and current sensor designs have been presented and evaluated. Through the use of these designs,
the single event tolerance of a digital system can be achieved at the expense of varying overhead
in terms of area, power, and delay
Radiation Tolerant Electronics, Volume II
Research on radiation tolerant electronics has increased rapidly over the last few years, resulting in many interesting approaches to model radiation effects and design radiation hardened integrated circuits and embedded systems. This research is strongly driven by the growing need for radiation hardened electronics for space applications, high-energy physics experiments such as those on the large hadron collider at CERN, and many terrestrial nuclear applications, including nuclear energy and safety management. With the progressive scaling of integrated circuit technologies and the growing complexity of electronic systems, their ionizing radiation susceptibility has raised many exciting challenges, which are expected to drive research in the coming decade.After the success of the first Special Issue on Radiation Tolerant Electronics, the current Special Issue features thirteen articles highlighting recent breakthroughs in radiation tolerant integrated circuit design, fault tolerance in FPGAs, radiation effects in semiconductor materials and advanced IC technologies and modelling of radiation effects
Soft-Error Resilience Framework For Reliable and Energy-Efficient CMOS Logic and Spintronic Memory Architectures
The revolution in chip manufacturing processes spanning five decades has proliferated high performance and energy-efficient nano-electronic devices across all aspects of daily life. In recent years, CMOS technology scaling has realized billions of transistors within large-scale VLSI chips to elevate performance. However, these advancements have also continually augmented the impact of Single-Event Transient (SET) and Single-Event Upset (SEU) occurrences which precipitate a range of Soft-Error (SE) dependability issues. Consequently, soft-error mitigation techniques have become essential to improve systems\u27 reliability. Herein, first, we proposed optimized soft-error resilience designs to improve robustness of sub-micron computing systems. The proposed approaches were developed to deliver energy-efficiency and tolerate double/multiple errors simultaneously while incurring acceptable speed performance degradation compared to the prior work. Secondly, the impact of Process Variation (PV) at the Near-Threshold Voltage (NTV) region on redundancy-based SE-mitigation approaches for High-Performance Computing (HPC) systems was investigated to highlight the approach that can realize favorable attributes, such as reduced critical datapath delay variation and low speed degradation. Finally, recently, spin-based devices have been widely used to design Non-Volatile (NV) elements such as NV latches and flip-flops, which can be leveraged in normally-off computing architectures for Internet-of-Things (IoT) and energy-harvesting-powered applications. Thus, in the last portion of this dissertation, we design and evaluate for soft-error resilience NV-latching circuits that can achieve intriguing features, such as low energy consumption, high computing performance, and superior soft errors tolerance, i.e., concurrently able to tolerate Multiple Node Upset (MNU), to potentially become a mainstream solution for the aerospace and avionic nanoelectronics. Together, these objectives cooperate to increase energy-efficiency and soft errors mitigation resiliency of larger-scale emerging NV latching circuits within iso-energy constraints. In summary, addressing these reliability concerns is paramount to successful deployment of future reliable and energy-efficient CMOS logic and spintronic memory architectures with deeply-scaled devices operating at low-voltages
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