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Hitachi, Renesas partner in 1.5V memory module

Posted: 22 Feb 2007 ?? ?Print Version ?Bookmark and Share

Keywords:Hitachi? Renesas Technology? phase change memory module? memory module?

Hitachi Ltd and Renesas Technology Corp. have developed a 512Kbyte phase change memory module operating at a 1.5V power supply voltage, which achieves 416KBps high-speed write and read speeds with a 20ns access time. Using the previously developed low-power phase change memory cells with a 100A write current, the two companies developed a peripheral circuit technology to enable the high-speed write and read operations.

The solution offers write circuit technology that enables high-speed writing with a small current. It features a data write scheme with two-step current control, enabling writing at 100A and below 100A, and generating Joule heat efficiently. Moreover, it has a serial write scheme which enables bits to be written serially one at a time. This prevents large peak currents which occur when multiple bits are written.

The phase change memory module also features high-speed read circuit supporting minute read current. The previous low-power phase change memory cells developed by the two companies have slow reading time due to the small readout current. To address this, a read circuit has been developed for the new module. The circuit in which a two-stage sense amplifier (amplification circuit) is used, and a signal is amplified gradually, optimizes the operating voltage of each sense amplifier. Compared with the use of a single-stage sense amplifier, amplification is performed in a shorter time, and a faster read time is achieved while suppressing the sense amplifier current consumption to 280A.

The memory solution also features circuit technology, which enables measurement of minute currents on the order of nano-amperes. The new circuit technology reduces current leakage to a minimum level by optimizing the memory circuit voltage, making it possible for the minute readout current of a memory cell to be measured with a high degree of accuracy. Feeding back measurement results to the manufacturing process makes it possible to contribute to improvements in memory cell quality.

The memory module was presented at the International Solid-State Circuits Conference in San Francisco early this month.

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