Shigeki Ohbayashi

A 500 MHz pipelined burst SRAM with improved SER immunity

One of the components key to increased mobile computer performance is level-2 (L2) cache memory, which is usually a high-frequency synchronous SRAM and typically consumes >2 W. This SRAM has to be housed in low-thermal-resistance package such as the plastic ball grid array (PBGA). Power dissipation must be reduced, since battery life is prolonged and a lower-cost TQFP package can be used. In addition, cosmic-ray-induced single soft errors are becoming a problem, since memory cell node capacitance is reduced with reduction of memory cell size. At high altitude (air flight level of 30000 ft), cosmic-ray-induced SER is increased by 2 orders of magnitude. This type of soft error is significant for mobile applications. The 64k x 36 synchronous pipelined burst SRAM (PBSRAM) described has lower power and improved SER immunity.

A 7 ns 1 Mb BiCMOS ECL SRAM with shift redundancy

A 7-Mb BiCMOS ECL (emitter coupled logic) SRAM was fabricated in a 0.8 mu m BiCMOS process. An improved buffer with a high-level output of nearly V/sub CC/ is adopted to eliminate the DC current in the level converter circuit, and the PMOS transistor has a wide operating margin in the level converter. The configurable bit organization is realized by using a sense-amplifier switch circuit with no access degradation. A wired-OR demultiplexer for the *1 output, having the same critical path as the *4 output circuit, allows for the same access time between the two modes. The *1 or *4 mode is electrically selected by the external signal. A simplified programming redundancy technology, shift redundancy, is utilized. Address programming is performed by cutting only one fuse in the shift redundancy. The RAM operates at the ECL-10K level with an access time of 7 ns. and the power dissipation at 50 MHz is 600 mW for the * mode. >

A 5.8-ns 256-Kb BiCMOS TTL SRAM with T-Shaped bit line architecture

Presents a new bit line architecture named T-shaped bit line architecture (TSBA), which is suitable for high speed, high density, and/or large bit-wide configuration SRAMs. TSBA, utilizing orthogonal complimentary bit lines in parallel with the word lines, is the solution to bit line pitch constraint for direct bipolar column sensing. This TSBA is applied to a 256-Kb SRAM with a typical access time of 5.8 ns. To achieve access times below 6 ns, this SRAM employs a bipolar Darlington column sense amplifier, a hierarchical column decoding scheme, a data bus shielding layout combined with TSBA, and a 0.8- mu m BiCMOS technology. >

New bit line architecture for ultra high speed SRAMs-T-shaped bit line and its real application to 256 k BiCMOS TTL SRAM

The authors propose a novel bit line architecture, the T-shaped bit line architecture (TSBA), which is suitable for high-speed, high-density and/or large bit-wide configuration SRAMs (static random-access memories). This architecture is applied to 256-kb BiCMOS TTL (transistor-transistor logic) I/O SRAM with a typical access time of 5.8 ns. To achieve sub-6-ns access time, a bipolar Darlington column sense amplifier, a global column decode technique, a shielded data bus technique with TSBA, and 0.8- mu m BiCMOS technology are employed.<<ETX>>