A 30-ns cycle time 4-Mb mask ROM

A 4-Mb mask ROM in a 256-Kb×16 organization is described. It is fabricated with a 1.0-μm CMOS process, using single polysilicon, two levels of metal, and 3.0×4.4 μm² X-cells. Unlike conventional ROM's, it implements a DRAM type RAS/CAS control scheme. A RAS access time of 60 ns is measured. For a fast data access, the chip has a consecutive address read mode in which the system needs to supply only a first address and subsequent addresses are generated in the ROM chip at every CAS clock. A 30-ns cycle time is demonstrated in this mode. 16-b data pins are also used for RAS/CAS multiplexed address inputs. Because of this three way pin multiplexing, the 7.5×10.5 mm² chip needs only 28 pins for its 400-mil SOJ package     

A 64K DRAM with 35 ns static column operation

A 64K dynamic RAM with a function mode similar to static memory operation is described. The device has multiplexed address inputs and a one-address strobe clock (RAS). After a row address is applied to the device, column selection is performed as in static memory, resulting in fast cycle time and simplicity of use. Column address access time and cycle times of 35 ns are achieved. The device has some other functions to reduce critical timings. Address transition detector circuits are used for column selection. An improved column decoder is provided to allow column address input skew. The device uses NMOS single transistor memory cells and is packaged in a standard 300-mil 16-pin DIP.     

A 16-ns 1-Mb CMOS EPROM

A 16-ns 1-Mb CMOS EPROM has been developed utilizing high-speed circuit technology and a double-metal process. In order to achieve the fast access time, a differential sensing scheme with address transition detection (ATD) is used. A double-word-line structure is used to reduce word-line delay. High noise immunity is obtained by a bit-line bias circuit and data-latch circuit. Sufficient threshold voltage shift (indispensable for fast access time) is guaranteed by a threshold monitoring program (TMP) scheme. The array is organized as 64 K×16 b, which is suitable for 32-b high-performance microprocessors. The active power is 425 mW, the programming time is 100 μs, and the chip size is 4.94×15.64 mm²     

A 62-ns 16-Mb CMOS EPROM with voltage stress relaxation technique

To meet the increasing demand for higher-density and faster EPROMs, a 16-Mb CMOS EPROM has been developed based on 0.6-μm N-well CMOS technology. In scaled EPROMs, it is important to guarantee device reliability under high-voltage operation during programming. By employing internal programming-voltage reduction and new stress relaxation circuits, it is possible to keep an external programming voltage V_pp of 12.5 V. The device achieves a 62-ns access time with a 12-mA operating current. A sense-line equalization and data-out latching scheme, made possible by address transition detection (ATD), and a bit-line bias circuit with two types of depletion load led to the fast access time with high noise immunity. This 16-Mb EPROM has pin compatibility with a standard 16-Mb mask-programmable ROM (MROM) and is operative in either word-wide or byte-wide READ mode. Cell size and chip size are 2.2 μm×1.75 μm and 7.18 mm×17.39 mm, respectively     

A high-speed 64K/spl times/4 CMOS DRAM using on-chip self-timing techniques

The duration of internal operation of this DRAM is controlled by on-chip self-timing signals. With this feature, the leading and trailing edges of the row address strobe are allowed to have timing windows of 16 and 11 ns, respectively, even at a minimum cycle time of 80 ns. A novel address decoding scheme, utilizing a combination of NMOS NOR row decoders, CMOS NAND column decoders, and common predecoders, is employed to realize a fast array access time and a small die. The RAM has been fabricated with a 1.2-/spl mu/m n-well CMOS technology, and has a 21.34-mm/SUP 2/ die. Typical row access and column address access times are 47 and 16 ns, respectively. The active power dissipation is 115 mW at 200-ns cycle time.     

A 16 ns 2K/spl times/8 bit full CMOS SRAM

A high-speed 2K/spl times/8 bit full CMOS SRAM fabricated with a platinum silicide gate electrode and single-level aluminum technology is described. A typical address access time of 16 ns, which is comparable to the 16-kb bipolar SRAMs, was achieved. Typical active and standby power dissipations are 150 mW and 25 nW, respectively. The platinum silicide word line reduces the total address access time by 25%. A compact cell layout design, as well as a 1.5-/spl mu/m device feature size, also gives fast access time. The properly controlled bit line swing voltage provides reliable and fast readout operation. The chip size of the SRAM is 2.7/spl times/3.5 mm.     

A 3.3-V 12-ns 16-Mb CMOS SRAM

A 16-Mb CMOS SRAM having an access time of 12 ns under a 3.3-V supply has been developed with a 0.4-μm process technology. An address access time of 12 ns has been achieved by an optimized architecture, the use of an automated transistor size optimizer, and a read-bus midlevel preset scheme (RBMIPS). For better yield and efficient testing, an on-chip test circuit with three test modes has been implemented     

A 16-Mb CMOS SRAM with a 2.3-μm2 single-bit-linememory cell

A novel architecture that enables fast write/read in poly-PMOS load or high-resistance polyload single-bit-line cells is developed. The architecture for write uses alternate twin word activation (ATWA) with bit-line pulsing. A dummy cell is used to obtain a reference voltage for reading. An excellent balance between a normal cell signal line and a dummy cell signal line is attained using balanced common data-line architecture. A newly developed self-bias-control (SBC) sense amplifier provides excellent stability and fast sensing performance for input voltages close to V_CC at a low power supply of 2.5 V. The single-bit-line architecture is incorporated in a 16-Mb SRAM, which was fabricated using 0.25-μm CMOS technology. The proposed single-bit-line architecture reduces the cell area to 2.3-μm² , which is two-thirds of a conventional two-bit-line cell with the same processes. The 16-Mb SRAM, a test chip for a 64-Mb SRAM, shows a 15-ns address access time and a 20-ns cycle time     

An eight-bit prefetch circuit for high-bandwidth DRAM's

A low-power and area-efficient data path circuit for high-bandwidth DRAMs is described. For fast burst read operations, eight data per data I/O are stored in local latches placed close to sense amplifiers. As implemented in a 16-Mb synchronous DRAM (SDRAM), this 8-b prefetch circuit allows an early precharge command and a fast access time because it provides low-capacitance data lines for segmented bit-line pairs. At a column address strobe (CAS) latency of two and a burst length of four, the SDRAM demonstrates 100-MHz seamless read operations from different row addresses, because the row precharge and read access latencies are hidden during the burst cycles. The layout of the prefetch circuit is not limited by the bit-line pitch, and data path circuits are connected by a second-metal layer over the memory cells. As a result, a small chip size of 99.98 mm² is attained. Low-capacitance data lines and small local latches result in low active power. In a 100-MHz full-page burst mode, the SDRAM with a 1 M×16-b configuration dissipates 60 mA at 3.6 V     

Two-13 ns-64K CMOS SRAM's with very low active power and improved asynchronous circuit techniques

64K/spl times/1 and 16K/spl times/4 CMOS SRAMs which achieve an access time of 13 ns and less than 12-mA active current at 10 MHz are described. A double-metal 1.5-/spl mu/m p-well process is used. A chip architecture with local amplification improves signal speed and data integrity. Address stability detection techniques are introduced as a method of assuring full asynchronicity over a wide range of conditions. A chip-select speed-up circuit allows high-speed access from a power-down mode. A memory cell design is presented which has improved layout efficiency (area of 189 /spl mu/m/SUP 2/), yet provides a very high cell ratio of 3:1 for signal stability and margin. Experimental results are presented which demonstrate full performance under address skews and other asynchronous input conditions. High-speed enable access and address access are observed over a wide range of operating conditions.     

A 3.5-ns, 500-mW, 16-kbit BiCMOS ECL RAM

A 16-kbit BiCMOS ECL SRAM with a typical address access time of 3.5 ns and 500-mW power dissipation was developed. The RAM was fabricated using half-micrometer, triple-poly, and triple-metal BiCMOS technology. The fast access time with moderate power dissipation has been achieved using new circuit techniques: a grounded-gate, nonlatching-type level converter with a wired-OR predecoder and a direct column sensing scheme having a cascode differential amplifier. As a result of extensive use of high-speed bipolar ECL circuits with self-aligned bipolar transistors, the RAM attains high-speed performance without degrading the low-power BiCMOS RAM characteristics.<>     

An 8 ns 4 Mb serial access memory

A new architecture for serial access memory is described that enables a static random access memory (SRAM) to operate in a serial access mode. The design target is to access all memory address serially from any starting address with an access time of less than 10 ns. This can be done by all initializing procedure and three new circuit techniques. The initializing procedure is introduced to start the serial operation at an arbitrary memory address. Three circuit techniques eliminate extra delay time caused by an internal addressing of column lines, sense amplifiers, word lines, and memory cell blocks. This architecture was successfully implemented in a 4-Mb CMOS SRAM using a 0.6 μm CMOS process technology. The measured serial access time was 8 ns at a single power supply voltage of 3.3 V     

A 12.5-ns 16-Mb CMOS SRAM with common-centroid-geometry-layoutsense amplifiers

A 16-Mb CMOS SRAM using 0.4-μm CMOS technology has been developed. This SRAM features common-centroid-geometry (CCG) layout sense amplifiers which shorten the access time by 2.4 ns. A flexible redundancy technique achieves high efficiency without any access penalty. A memory cell with stacked capacitors is fabricated for high soft-error immunity. A 16-Mb SRAM with a chip size of 215 mm² is fabricated and an address access time of 12.5 ns has been achieved     

A 6-ns 4-Mb CMOS SRAM with offset-voltage-insensitive current senseamplifiers

A 4-Mb CMOS SRAM with 3.84 μm² TFT load cells is fabricated using 0.25-μm CMOS technology and achieves an address access time of 6 ns at a supply voltage of 2.7 V. The use of a current sense amplifier that is insensitive to its offset voltage enables the fast access time. A boosted cell array architecture allows low voltage operation of fast SRAM's using TFT load cells     

A circuit technology for sub-10-ns ECL 4-Mb BiCMOS DRAM's

The feasibility of realizing an emitter-coupled-logic (ECL) interface 4-Mb dynamic RAM (DRAM) with an access time under 10 ns using 0.3-μm technology is explored, and a deep submicrometer BiCMOS VLSI using this technology is proposed. Five aspects of such a DRAM are covered. They are the internal power supply voltage scheme using on-chip voltage limiters, an ECL DRAM address buffer with a reset function and level converter, a current source for address buffers compensated for device parameter fluctuation, an overdrive rewrite amplifier for realizing a fast cycle time, and double-stage current sensing for the main amplifier and output buffer. Using these circuit techniques, an access time of 7.8 ns is expected with a supply current of 198 mA at a 16-ns cycle time     

New nibbled-page architecture for high-density DRAMs

A nibbled-page architecture which can be used to access all column addresses on the selected row address randomly in units of 8 bits at the 100 Mbit/s data rate is discussed. To realize such high-speed architecture, three key circuit techniques have been developed. An on-chip interleaved circuit has been used for the high-speed serial READ and WRITE operations. Column address prefetch and WE signal prefetch techniques have been introduced to eliminate idle time between 8 bit units. The nibbled-page architecture has been successfully implemented in an experimental 16 Mb DRAM, and 100 Mb/s operation has been achieved. The DRAM with nibbled-page mode is very effective in simplifying the design of high-speed data transfer systems     

A 38-ns 4-Mb DRAM with a battery-backup (BBU) mode

The authors describe a DRAM with a battery-backup (BBU) mode, which allows automatic data retention with extremely reduced power consumption. The circuit techniques for reducing the refresh current and the back-bias-generator current are shown. The dissipated current required for data retention of 44 μA is achieved under typical conditions. This DRAM was fabricated with quad-poly and double-metal CMOS process technology. The memory array is divided into 4×32 subarrays. The finely divided array architecture is suitable for the fast access time and the multibit test mode     

A 9-ns 1-Mbit CMOS SRAM

A 1-Mbit CMOS static RAM (SRAM) with a typical address access time of 9 ns has been developed. A high-speed sense amplifier circuit, consisting of a three-stage PMOS cross-coupled sense amplifier with a CMOS preamplifier, is the key to the fast access time. A parallel-word-access redundancy architecture, which causes no access time penalty, was also incorporated. A polysilicon PMOS load memory cell, which had a large on-current-to-off-current ratio, gave a much lower soft-error rate than a conventional high-resistance polysilicon load cell. The 1-Mbit SRAM, fabricated using a half-micrometer, triple-poly, and double-metal CMOS technology, operated at a single supply voltage of 5 V. An on-chip power supply converter was incorporated in the SRAM to supply a partial internal supply voltage of 4 V to the high-performance half-micrometer MOS transistors.<>     

An effective BIST scheme for SRAM full speed test

This article presents a novel built-in self-test (BIST) scheme at full speed test where access time test is performed. Based on normal BIST circuits, we harness an all digital phase locked loop to generate a high-frequency clock for static random access memory (SRAM) performance test at full speed. A delay chain is incorporated to achieve the four-phase clock. As inputs to SRAM, clock, address, data are generated in terms of the four-phase clock. Key performance parameters, such as access time, address setup and hold times, are measured. The test chip has been fabricated by United Microelectronics Corporation 55?nm CMOS logic standard process. According to test results, the maximum test frequency is about 1.3?GHz, and the test precision is about 35?ps at the typical process corner with supply voltage 1.0?V and temperature 25°C.     

AC-and DC-powered subnanosecond 1-kbit Josephson cache memorydesign

The address decoders, address line drivers, and sense circuits of the fully decoded memory consist of resistor-coupled Josephson logic circuits to realize fast access. The memory cell is constructed from two three-junction symmetric SQUID (superconducting quantum interface device) gates, and a four-flux-quanta storage loop for enabling bipolar current drive. This memory configuration has intrinsic advantages in regard to magnetic flux trapping in address lines and a gate circuit latch-up problem over a DC-powered memory constructed from inductor coupled gates. Individual control and cell circuits were fabricated, using a lead-alloy process, and their operation was verified. A 570-ps read access time is estimated as the sum measured 280-ps decoding time, and calculated 130-ps address line current rising time, 110-ps sense time, and 50-ps signal propagation time. The 1-kb chip is designed to consume 9 mW without voltage regulators