Reduction of Power Consumption in FPGAs - An Overview <s> I. INTRODUCTION <s> An antifuse is an electrically programmable two-terminal device with small area and low parasitic resistance and capacitance. Field-programmable gate arrays (FPGAs) using antifuses in a segmented channel routing architecture now offer the digital logic capabilities of an 8000-gate conventional gate array and system speeds of 40-60 MHz. A brief survey of antifuse technologies is provided. the antifuse technology, routing architecture, logic module, design automation, programming, testing and use of ACT antifuse FPGAs are described. Some inherent tradeoffs involving the antifuse characteristics, routing architecture and logic module are illustrated. > <s> BIB001 </s> Reduction of Power Consumption in FPGAs - An Overview <s> I. INTRODUCTION <s> Modern field programmable gate arrays (FPGAs) provide embedded memory blocks (EMBs) to be used as on-chip memories. In this paper, we explore the possibility of using EMBs to implement logic functions when they are not used as on-chip memory. We propose a general technology mapping problem for FPGAs with EMBs for area and delay minimization and develop an efficient algorithm based on the concepts of Maximum Fanout Free Cone (MFFC) [3] and Maximum Fanout Free Subgraph (MFFS) [7], named EMB_Pack, which minimizes the area after or before technology mapping by using EMBs while maintaining the circuit delay. We have tested EMB_Pack on MCNC benchmarks on Altera's FLEX10K device family [1]. The experimental results show that compared with the original mapped circuits generated from CutMap [5] without using EMBs, EMB_Pack as postprocessing can further reduce up to 10% of the area on the mapped circuits while maintaining the layout delay by making efficient use of available EMB resources. Compared with CutMap-e without using EMBs, EMB_Pack as pre-mapping processing followed by CutMap-e can reduce 6% of the area while maintaining the circuit optimal delay. <s> BIB002 </s> Reduction of Power Consumption in FPGAs - An Overview <s> I. INTRODUCTION <s> From the Publisher: ::: Architecture and CAD for Deep-Submicron FPGAs addresses several key issues in the design of high-performance FPGA architectures and CAD tools, with particular emphasis on issues that are important for FPGAs implemented in deep-submicron processes. Three factors combine to determine the performance of an FPGA: the quality of the CAD tools used to map circuits into the FPGA, the quality of the FPGA architecture, and the electrical (i.e. transistor-level) design of the FPGA. Architecture and CAD for Deep-Submicron FPGAs examines all three of these issues in concert. <s> BIB003 </s> Reduction of Power Consumption in FPGAs - An Overview <s> I. INTRODUCTION <s> A highly scalable flash-based Field Programmable Gate Array (FPGA) technology has been achieved with Deep Trench Isolation (DTI). The DTI allows for a reduced cell size and enables Independent Pwell (IPW) operation. The IPW allows the Fowler-Nordheim (FN) Uniform Channel Program and Erase (UCPE) with less than plusmn10 V. Additionally, the IPW approach allows a greater flexibility in the array bias scheme reducing the gate disturb during programming and eliminating all Gate-Induced Drain Leakage (GIDL) conditions. Characterization of a FPGA cell and 0.5 Mbit array with 90 nm design rules is demonstrated with excellent electrical characteristics. <s> BIB004
Field-Programmable Gate Arrays (FPGAs) are integrated circuits (ICs) that can be programmed to implement any digital circuit. The main difference between FPGAs and conventional fixed logic implementations, such as Application Specific Integrated Circuits (ASICs), is that the designer can program the FPGA on-site. Moreover, using an FPGA instead of a fixed logic implementation eliminates the non-recurring engineering (NRE) costs and significantly reduces timeto-market. Hence, FPGAs are highly desirable for implementation of digital systems due to their flexibility, programmability and low end product life cycle and all this makes them ideal for prototyping, debugging, and for small to medium volume applications. FPGAs are slower and less efficient than fixed implementation, due to the added circuitry that is needed to make them very flexible. In FPGA, programmable switches controlled by configuration memory occupy a large area and add a significant amount of parasitic capacitance and resistance to the logic and routing resources. As a result, FPGAs are approximately 3 times slower, 20 times larger, and 12 times less power efficient compared to ASICs  . The area overhead, combined with research and development costs, increases the per-unit cost of FPGAs, which makes them less suited for high-volume applications. Moreover, the speed and power overhead precludes the use of FPGAs for high-speed or low-power applications. In more than 20 years since the introduction of FPGA, research and development has produced dramatic improvements in FPGA speed and area efficiency, narrowing the gap between FPGAs and ASICs and making FPGAs the platform of choice for implementing digital circuits. FPGAs hold significant promise as a fast to market replacement for ASICs in many applications. A significant number of studies include focus on faster and more area efficient programmable routing resources. Some important advancements have also been made in respect of CAD tools that are used to map applications onto the programmable fabric of FPGA. The Versatile Place and Route (VPR) tool described in BIB003 , yields significant improvements in performance by improving on the existing clustering, placement, and routing algorithms. Logic-to-memory mapping tools, described in BIB002 -  , shows improvement in the area efficiency of FPGAs with embedded memories wherein parts of the application are packed into unused memories before mapping the rest of the application into logic elements. In recent years, the main focus of the research has been shifting to lower the power consumption. Power consumption is an important part of equation determining the product size, weight and efficiency. Unfortunately, the advantages of FPGAs are offset in many cases by their high power consumption and area. The improved reliability, lower operating and cooling costs, and the ever-growing demand for low-power portable communications and computer systems, is motivating new low power techniques, especially for FPGAs, which dissipate significantly more power than fixed-logic implementations. Indeed, the International Technology Roadmap for Semiconductors (ITRS) has identified lowpower design techniques as a critical technology need  . This paper aims to describe the general techniques used to reduce the power dissipation and review the work carried out in this area and has been organized in further four sections. The basic architecture and hardware structure of FPGA has been discussed in 2 followed by its logic resources architecture and routing resources architecture in 2.1 and 2.2. CAD tool for FPGAs along II. FPGA ARCHITECTURE, ITS HARDWARE STRUCTURE FPGAs consist of a two-dimensional array of programmable logic blocks that are connected through a configurable interconnection fabric. Figure 1 (a) provides an abstract view of an FPGA. As illustrated, prefabricated routing tracks are arranged in channels that are interspersed between rows and columns of logic blocks. Today's commercial FPGAs use look-up tables (LUTs) as the base element for implementing combinational logic functions, and contain flip-flops for implementing sequential logic. A K-input LUT (K-LUT) is a small memory capable of implementing any logic function that uses, at most, K inputs. A simplified FPGA logic block is shown in Figure 1 Modern FPGAs consist of programmable logic resources embedded in a sea of programmable interconnects. The programmable logic resources can be configured to implement any logic function, while the interconnects provide the flexibility to connect any signal in the design to any logic resource. The programming technology for the logic and interconnect resources can be Static Random Access Memory (SRAM), flash memory BIB004 , or antifuse  BIB001 . SRAM-based FPGAs offer incircuit reconfigurability at the expense of being volatile, while antifuse are write-once devices. Flash-based FPGAs provide an intermediate alternative by providing reconfigurability as well as non-volatility. The most popular programming technology in state-of-the-art FPGAs is SRAM. Traditionally, FPGAs consist of input/output pads, logic resources, and routing resources. However, state-ofthe-art FPGAs usually include embedded memory, DSP blocks, Phase-Locked Loops (PLLs), embedded processors, and other special feature blocks, as shown in Figure 2 . These features allowed FPGAs to be an attractive alternative for some SoPC designs. The next Sections shed light on some of the available commercial FPGA architectures and FPGA CAD flow.