Trends in megabit DRAM circuit design

The state of the art in megabit dynamic random access memory (DRAM) circuit and chip design is reviewed in terms of essential design parameters such as signal-to-noise ratio, power dissipation, and speed. The memory cell signal charge has decreased gradually with an increase in memory cell size, despite the vertically structured cell designs. To offset this decrease, multidivided data-line structures, low-power design, and transposition of folded data lines are essential. To reduce power dissipation, an increase in the maximum refresh cycle and multidivided data lines combined with shared I/O in addition to a reduced operating voltage are efficient. A BiCMOS circuit provides a high-speed access time with low cost due to the high drivability of the driver and high sensitivity of the amplifier. It is predicted that the current DRAM technology might be diversified in the future so that a large-memory-capacity-oriented technology would coexist with a high-speed-oriented technology, posing power-supply standardization as a continuing serious concern     

A submicrometer megabit DRAM process technology using trench capacitors

This paper describes guidelines for developing a 1-4-Mbit DRAM process, and device/process technologies for fabricating an experimental 1-Mbit DRAM. A single transistor cell combined with a trench capacitor and on-chip ECC technologies has the potential to realize a cell size of 10 µm²without degrading soft error immunity. A depletion trench capacitor, submicrometer n-well CMOS process, Mo-poly gate, and submicrometer pattern formation technologies are developed, and an experimental 1-Mbit DRAM with a cell size of 20 µm²is successfully developed by using these technologies.     

A multibit test trigger circuit for megabit SRAMs

A multibit test (MBT) trigger circuit for megabit SRAM packages with no unused pins is discussed. The features of the MBT trigger circuit are a logic trigger mode without using any additional pins and practical use of counter circuits. The essence of trigger mode selection is that two pulses are for MBT set and three pulses are for MBT reset. In this way, a logic trigger mode that does not use NC pins is especially effective as a 4-Mb SRAM. In addition, the proposed scheme is able to act as a logic trigger for an MBT circuit. The scheme is simple and effective. The logic trigger mode is proposed for future standardization     

High-speed DRAM architecture development

This paper is an overview of the high-speed DRAM architecture developments. We discuss developments on density growth, interface technology, memory-core architecture, and DRAM+ASIC technology. We can find the developments of density as 2× growth instead of 4× by each generation. Interface technologies will have a tendency to use the terminated bus structure for higher data rate. Memory-core architecture developments are the trials for actual bandwidth improvements. DRAM+ASIC technologies seem to require universal interface solutions. We tried to show that no single solution is able to cover the wide diversity of future system requirements     

用Cadence PSD软件做高速电路设计

提出高速电路设计所面临的问题,介绍利用Cadence PSD(PCB System Design)软件做高速电路设计的方法和简要过程,给出了一个设计实例和测试结果,列举了使用Cadence PSD软件做高速电路设计的优点。     

A circuit design of intelligent cache DRAM with automaticwrite-back capability

An intelligent cache based on a distributed architecture that consists of a hierarchy of three memory sections-DRAM (dynamic RAM), SRAM (static RAM), and CAM (content addressable memory) as an on-chip tag-is reported. The test device of the memory core is fabricated in a 0.6 μm double-metal CMOS standard DRAM process, and the CAM matrix and control logic are embedded in the array. The array architecture can be applied to 16-Mb DRAM with less than 12% of the chip overhead. In addition to the tag, the array embedded CAM matrix supports a write-back function that provides a short read/write cycle time. The cache DRAM also has pin compatibility with address nonmultiplexed memories. By achieving a reasonable hit ratio (90%), this cache DRAM provides a high-performance intelligent main memory with a 12 ns(hit)/34 ns(average) cycle time and 55 mA (at 25 MHz) operating current     

一种高可靠点火执行级电路的设计

火工品点火技术是一种对安全性和可靠性要求极高的技术,一般是一个系统中最关键的执行环节,如果出现问题,轻则导致系统试验失败,重则导致人员伤亡。为了可靠的实现火工品的点火,提出了一种高可靠点火执行级电路的设计方案,通过对点火准备指令、点火指令等信号的可靠接收和滤波,基于点火准备指令的两级延时保护,点火的执行部分多重安全保护等方法,安全准确地实现了对火工品的点火控制,并在某型空空导弹点火装置中得到应用,取得了良好的效果。     

A circuit design to suppress asymmetrical characteristics inhigh-density DRAM sense amplifiers

A circuit design technique for suppressing asymmetrical characteristics in a high-density DRAM sense amplifier is discussed, and the effect of drain current imbalances between transistor pairs and the sensitivity of the sense amplifier are studied experimentally. A sense amplifier composed of parallel transistor pairs which have a reversed source and drain arrangement on a wafer is capable of suppressing the asymmetry effects to less than 15 mV in a range of submicrometer gate lengths and of reducing the layout area by about 43% compared with the conventional sense amplifier     

256-Mb DRAM circuit technologies for file applications

256-Mb DRAM circuit technologies characterized by low power and high fabrication yield for file applications are described. The newly proposed and developed circuits are a self-reverse-biasing circuit for word drivers and decoders to suppress the subthreshold current to 3% of the conventional scheme, and a subarray-replacement redundancy technique that doubles chip yield and consequently reduces manufacturing costs. An experimental 256-Mb DRAM has been designed and fabricated by combining the proposed circuit techniques and a 0.25-μm phase-shift optical lithography, and its basic operations are verified. A 0.72-μm² double-cylindrical recessed stacked-capacitor (RSTC) cell is used to ensure a storage capacitance of 25 fF/cell. A typical access time under a 2-V power supply voltage was 70 ns. With the proper device characteristics, the simulated performances of the 256-Mb DRAM operating with a 1.5-V power supply voltage are a data-retention current of 53 μA and an access time of 48 ns     

An open-loop clock deskewing circuit for high-speed synchronous DRAM

An open-loop clock deskewing circuit (CDC) for high-speed synchronous DRAM is described. Unlike the conventional circuits, the CDC does not require an additional measure delay line, thus power consumption is reduced. The delay is measured directly from the main delay line and both the input and output ports of the delay line are movable. The CDC provides a deskewed clock within two clock cycles.     

A full bit prefetch DRAM sensing circuit

A DRAM sensing circuit that achieves both a fast RAS access time and a high-bandwidth burst operation is proposed. For the data burst capability of synchronous DRAM's, 256-bit-long data I/O lines are divided into eight segments. A small local latch is provided for each segment of 32 bit-line pairs to prefetch eight data out of the 256 sense amplifiers. A local buffer is connected to eight local latches through selection switches. Burst read operations, up to eight bits, are done by activating selection switches and the local buffer serially. Besides this prefetch capability, the segmented data I/O line results in very small capacitance, only 0.09 pF. The sensing scheme uses nMOS bit switches and a full Vdd precharge voltage for bit and segmented data I/O lines. Then, after sense amplifiers are turned on, only low-going bit lines are connected to the segmented data I/O lines without any voltage disturbance because of the small capacitance. The proposed circuit, therefore, realizes a high-speed RAS access, which is 16 ns faster than a conventional DRAM. A circuit layout design based on a 0.5-μm design rule shows no area impact     

High-speed charge transfer sense amplifier for 0.5 V DRAM array applications

A new high-speed charge transfer sense amplifier scheme is proposed for 0.5 V DRAM array applications. The combination of both the cross-coupled structure and the boosting capacitance used in the proposed sense amplifier leads to a maximum voltage difference between sense nodes. Based on post-layout simulations, the charge transfer speed and the voltage difference after charge transfer are improved 40.7% and 59.29%, respectively, over the prior art circuits. The power-delay product is then enhanced 38.26%. Besides, both high voltage pre-charge levels and high voltage control signals are not required in this proposed circuit as compared with prior arts.     

Noise-generation analysis and noise-suppression design techniques in megabit DRAMs

A detailed noise-generation model of peak current and voltage-bouncing noise for DRAMs is presented. This model was found to be a very effective tool for predicting and analyzing quantitative bouncing noise level in noise-suppress circuit design, especially for high-performance high-density DRAMs. The resulting performance for the fabricated NMOS 1-Mb DRAM is 100-mA peak current, 6-mA/ns current transition rate, and 0.27-V output voltage-bouncing noise for a standard system board.     

High-speed CMOS circuit technique

It is shown that clock frequencies in excess of 200 MHz are feasible in a 3-μm CMOS process. This performance can be obtained by means of clocking strategy, device sizing, and logic style selection. A precharge technique with a true single-phase clock, which increases the clock frequency and reduces the skew problems, is used. Device sizing with the help of an optimizing program improves circuit speed by a factor of 1.5-1.8. The logic depth is minimized to one instead of two or more, and pipeline structures are used wherever possible. Experimental results for several circuits which work at clock frequencies of 200-230 MHz are presented. SPICE simulation shows that some circuits could work up to 400-500 MHz     

高速低功耗FPGA的应用设计

现场可编程序门阵列(FPGA)是开发专用集成电路的有效手段,本文提出了一种基于Actel FPGA的高速、低功耗的应用设计技术,实践证明,效果良好.     

Concordant memory design: an integrated statistical design approach for multi-gigabit DRAM

Concordant memory design incorporates fluctuation in device parameters statistically into signal-to-noise ratio analysis in DRAM. In this design, the effective signal voltage of all cells in a chip is calculated, and the failed bit count of the chip is estimated. The proposed design approach gives us a quantitative evaluation of the memory array and assures 1.4-V array operation of 100-nm-1-Gb DRAM. Calculated dependence of the failed bit count on the array voltage is in close agreement with measured data for the 512-Mb DRAM chip.     

High-speed low-power Darlington ECL circuit

Presents an ECL circuit with a Darlington configured dynamic current source and active-pull-down emitter-follower stage for low-power high-speed gate array application. The dynamic current source provides a large dynamic current during the switching transient to improve the power delay of the logic stage (current switch). A novel self-biasing scheme for the dynamic current source and the active-pull-down transistor with no additional devices and power in the biasing circuit is described. Based on a 0.8-μm double-poly self-aligned bipolar technology at a power consumption of 1 mW/gate, the circuit offers 28% improvement in the loaded (FI/FO=3, C_L=0.3 pF) delay and 42% improvement in the load driving capability compared with the conventional ECL circuit. The design and scaling considerations of the circuit are discussed     

High-speed GaAs SDFL divider circuit

High-speed divider circuits find numerous applications in prescalers for counters, frequency synthesizers, and digital phase locked loops. To accommodate these applications, a high-speed multimode divider circuit has been designed, fabricated, and tested. This circuit, fabricated on semi-insulating Gallium Arsenide substrates, and utilizing Schottky diode FET logic (SDFL) technology, has been tested at a maximum clock frequency of 1.84 GHz. High yields of circuits operating over 1 GHz have been obtained over a number of wafers.     

High-speed circuit designs for transmitters in broadband data links

Various high-speed techniques including internal peaking, differentially stacked inductor, and dual-loop PLL for wireline communications are proposed,analyzed, and verified by means of three independent circuits. A multiplexer incorporates multiple peaking techniques and gate control switching to achieve an operation speed of 20 Gb/s while consuming 22 mW from a 1.8-V supply. A voltage-controlled oscillator employing differentially stacked inductor accomplishes a phase noise of -90dBc/Hzat 1-MHz offset with a minimum power of 1 mW. A clock multiplication unit utilizes dual-loop architecture as well as a third-order loop filter, arriving at an output jitter of 0.2 ps, rms (0.87 ps, rms de-embedding 0.84 ps, rms from the instruments) and 4.5 ps, pp while consuming 40 mW from a 1.8-V supply.     

High-speed and high-precision current winner-take-all circuit

A CMOS high-performance current-mode winner-take-all circuit is presented. The circuit employs a novel technique for inhibitory and excitatory feedbacks based on input currents average computation, achieving both high speed and high precision. The circuit is designed for operation with a wide range of input current values, allowing its integration with circuits operating both in subthreshold and in strong inversion regions. Two circuits, each for a different range of input currents, have been implemented in a standard 0.35-/spl mu/m CMOS process available through MOSIS and are operated via a 3.3-V supply. Their operation is discussed, simulation results are reported and preliminary measurements from a test chip are presented.