Mitsubishi unveils DRAM in thin film transistor LCD

ITworld.com |  Hardware

Mitsubishi Electric Corp. unveiled a prototype Wednesday of a new LCD (liquid
crystal display) panel for cellular telephones that the company says offers a
large number of colors with low power consumption.

The company is claiming an industry first for the new display which is a development
of polysilicon TFT (thin film transistor) LCD technology and includes embedded
DRAM (dynamic random access memory) alongside each pixel. It was put on show
at EDEX, the Electronic Display Exhibition, which opened Wednesday in Tokyo.

Embedded memory in such displays is a recent development. Engineers found that
power consumption could be cut by adding memory to each pixel although until
now display manufacturers have been experimenting with adding a single bit of
SRAM (static random access memory) to each pixel.

Mitsubishi announced Wednesday it has succeeded in embedding 4 bits of DRAM
alongside each pixel. The 4 bits of memory are enough to support 4,096 colors
in standby mode and over 65,000 colors in normal mode -- several steps up from
the embedded SRAM types which support eight colors and 4,096 colors respectively.
Additionally, the company said the 4 bits of DRAM take up approximately the
same space as a single SRAM bit which means screen resolution is not sacrificed.

The new displays are being developed for use in cellular telephones because
of demands from phone makers for screens that consume small amounts of power
while being able to display many colors. The prototype screen on show from Mitsubishi
was a 2.27 inch reflective type that consumed 4 milliwatts of power in standby
mode. Engineers are working to reduce this further before commercialization.

Also at EDEX, Toshiba Corp. and Sanyo Electric Co. Ltd. were displaying prototype
reflective polysilicon TFT LCDs with embedded SRAM. Toshiba offered few details
on its 2 inch prototype although Sanyo was a little more forthcoming. It claimed
power consumption in standby eight-color mode of 0.07 milliwatts for its 2.1
inch screen. In contrast a conventional polysilicon display with no memory consumes
around 1.7 milliwatts, Toshiba said.

More information on EDEX 2001, which runs until Friday at Tokyo Big Sight,
can be found online at http://edex-ess.jesa.or.jp/.

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