강석형 교수

Approximation can increase performance or reduce power consumption with a simplified or inaccurate circuit in application contexts where strict requirements are relaxed. For applications related to human senses, approximate arithmetic can be used to generate sufficient results rather than absolutely accurate results. Approximate design exploits a tradeoff of accuracy in computation versus performance and power. However, required accuracy varies according to applications, and 100% accurate result

We propose a logic synthesis methodology with a novel low-power circuit structure for ternary logic. The proposed methodology synthesizes a ternary function as a ternary logic gate using carbon nanotube field-effect transistors (CNTFETs). The circuit structure uses the body effect to mitigate the excessive power consumption for the third logic value. Energy-efficient ternary logic circuits are designed with a combination of synthesized low-power ternary logic gates. The proposed methodology is a

Current processor designs have a critical operating point that sets a hard limit on voltage scaling. Any scaling beyond the critical voltage results in exceeding the maximum allowable error rate, i.e., there are more timing errors than can be effectively and gainfully detected or corrected by an error-tolerance mechanism. This limits the effectiveness of voltage scaling as a knob for reliability/power tradeoffs. In this paper, we present power-aware slack redistribution, a novel design-level app

Modern digital IC designs have a critical operating point, or “wall of slack”, that limits voltage scaling. Even with an error-tolerance mechanism, scaling voltage below a critical voltage - so-called overscaling - results in more timing errors than can be effectively detected or corrected. This limits the effectiveness of voltage scaling in trading off system reliability and power. We propose a design-level approach to trading off reliability and voltage (power) in, e.g., microprocessor designs

The well-studied gate-sizing optimization is a major contributor to IC power-performance tradeoffs. Viable optimizers must accurately model circuit timing, satisfy a variety of constraints, scale to large circuits, and effectively utilize a large (but finite) number of possible gate configurations, including Vt and Lg. Within the research-oriented infrastructure used in the ISPD 2012 Gate Sizing Contest, we develop a metaheuristic approach to gate sizing that integrates timing and power optimiza

Aggressive requirements for low power and high performance in VLSI designs have led to increased interest in approximate computation. Approximate hardware modules can achieve improved energy efficiency compared to accurate hardware modules. While a number of previous works have proposed hardware modules for approximate arithmetic, these works focus on solitary approximate arithmetic operations. To utilize the benefit of approximate hardware modules, CAD tools should be able to quickly and accura

Ternary logic circuit has been studied for several decades because it can provide simpler circuits and subsequently lower power consumption via succinct interconnects. We demonstrated a ternary full adder exhibiting a low power-delay-product of ~10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-16</sup> J, which is comparable to the binary equivalent circuit. The ternary full adder was modeled using device parameters extracted from the experimenta

Incremental static timing analysis (iSTA) is the backbone of iterative sizing and Vt-swapping heuristics for post-layout timing recovery and leakage power reduction. Performing such analysis through available interfaces of a signoff STA tool brings efficiency and functionality limitations. Thus, an internal iSTA tool must be built that matches the signoff STA tool. A key challenge is the matching of “black-box” modeling of interconnect effects in the signoff tool, so as to match wire slew, wire

Over the last few decades, CMOS-based digital circuits have been steadily developed. However, because of the power density limits, device scaling may soon come to an end, and new approaches for circuit designs are required. Multi-valued logic (MVL) is one of the new approaches, which increases the radix for computation to lower the complexity of the circuit. For the MVL implementation, ternary logic circuit designs have been proposed previously, though they could not show advantages over binary

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Conventional CAD methodologies optimize a processor module for correct operation, and prohibit timing violations during nominal operation. In this paper, we propose recovery-driven design, a design approach that optimizes a processor module for a target timing error rate instead of correct operation. We show that significant power benefits are possible from a recovery-driven design flow that deliberately allows errors caused by voltage overscaling ([10],[3]) to occur during nominal operation, wh

The proliferation of embedded systems and mobile devices has created an increasing demand for low-energy hardware. Dynamic voltage and frequency scaling (DVFS) is a popular energy reduction technique that allows a hardware design to reduce average power consumption while still enabling the design to meet a high-performance target when necessary. To conserve energy, many DVFS-based embedded and mobile devices often spend a large fraction of their lifetimes in a low-power mode. However, DVFS desig

This article presents a cryo-CMOS quantum controller IC for superconducting qubits. The proposed globally synchronized clock system internally generates different local oscillator (LO) frequencies using multiple phase-locked loops (PLLs) driven by a common reference clock. It provides flexibility in spectral management as well as scalability for expansion to a large-scale quantum controller. The test chip includes two PLLs, four pulse modulator channels, and two receiver channels. Implemented ch

Extensive research on quantum mechanics in past decades has successfully paved the way towards the disruptive technology of quantum computing. A further step to the realization of a fault-tolerant scalable quantum computer is presenting challenges in the field of engineering. It necessitates a microsystem operating at 4K in a dilution refrigerator, which would be inevitable to control thousands or millions of qubits sitting at 10mK. There have been IC implementations of pulse modulators generati

Multiple-valued logic (MVL) has potential advantages for energy-efficient design by reducing a circuit complexity. Because of physical device and circuit realization issues, however, there are relatively small number of researches on MVL circuit designs. We design a novel ternary multiplier based on a ternary CMOS (T-CMOS) compact model. To estimate performance and energy efficiency of our ternary design, we construct a standard ternary-cell library and exploit a ternary static timing analysis (