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News Release

July 27, 1998

Hitachi Releases Graphic Liquid Crystal Controller/Driver Enabling Switching between 112 x 80-Dot Graphic Display and 10-line/16-digit Character Display

-Enables large-screen liquid crystal display in compact portable communication products, etc.-

Hitachi, Ltd. (NYSE:HIT) today announced the HD66728 graphic liquid crystal controller/driver for liquid crystal display systems in mobile communication products such as digital portable, PHS, and digital cordless phones, offering the capability of switching between a 112 x 80-dot graphic display*1 (the largest in this class) and a 10-line/16-digit character display*2 with a single-chip. Sample shipments will begin in August 1998 in Japan. The HD 66728's ability to handle an 80-dot vertical screen display enables a large-screen LCD to be incorporated without increasing the horizontal width of the system.

COG*3, COF*4, and TCP*5 mounting types are available to meet the needs of different users.

With the rapid growth of the market for mobile communication products such as portable and PHS phones, there are constant demands for lower power consumption, greater multifunctionality, reduced size and weight, and lower costs.

And with the increasing multifunctionality and higher added value of the small LCD panels used in these products, it has become necessary to provide a large-screen-size graphic display to implement additional functions such as kanji message communication, e-mail, games, and scheduler facilities, as well as the conventional phone number display and directory functions.

Typical single-chip graphics LCD controller/drivers in this class have previously supported a display size of 132 dots horizontally by 65 dots vertically. However, since the sets themselves must be small and lightweight in the case of mobile communication products such as portable phones, the products need to be slim in design, and this has limited the display size that can actually be used by the graphic LCD controller/driver to around 96 x 65 dots. With a 16 x 16-dot kanji font, this display size allows only 24 characters to be displayed (4 lines x 6 digits), insufficient for acceptable kanji message communication or e-mail.

In response to this problem, Hitachi has developed the HD 66728 graphic LCD controller/driver which enables the display size to be extended vertically (in which direction the mounting area is less restricted due to the set construction), allowing the simultaneous display of a large amount of information on a 112 x 80-dot screen.

Using a 12 x 13-dot kanji font, up to 54 characters (6 lines x 9 digits) can be displayed within the LCD screen, enabling services such as kanji messaging and e-mail to be offered. Like the 72 x 26-dot graphic display HD66724, 96 x 26-dot HD66725, and 96 x 42-dot HD66726 currently in production, the HD66728 is also capable of displaying standard alphanumeric and kana characters.

As the HD66728 extends the display size vertically, the LCD drive duty is higher. Generally speaking, a higher LCD drive duty is associated with such side effects as a higher LCD drive voltage, lower display quality, and increased current dissipation, but the HD66728 includes features to keep such side effects to a minimum.

For example, to handle the higher drive voltage, a step-up circuit is included that generates an LCD drive voltage up to 5 times the system supply voltage. This enables a drive voltage of approximately 15V to be obtained in a 3V system. In addition, since the LCD drive bias ratio is software-programmable, the bias ratio can be kept low through the use of liquid crystal materials with excellent on/off transient characteristics, thus enabling the LCD drive voltage itself to be reduced.

To prevent a drop in display quality, the drive capacity of the LCD drive voltage generation op-amp has been increased, and the on-resistance of each driver output has also been kept low. Also, to reduce crosstalk noise generated on the LCD screen, the HD66728 uses the C-pattern LCD drive method employed in large liquid crystal display systems. With the C-pattern LCD drive method, the alternation frequencies of illuminated and non-illuminated parts of the LCD are equalized by performing liquid crystal alternating drive for multiple lines at one time, so reducing the contrast fluctuations associated with alternation frequency deviation.

To reduce power consumption, a partial display function is incorporated that allows only part of the screen display area to be driven. Total power consumption for full-screen display is 420 microwatts (at 3V operation), but only 210 microwatts (at 3V operation) with partial display drive. Use of this partial display function during system standby and waiting periods enables power consumption to be cut by approximately 50%, greatly extending battery life.

The HD66728 includes a synchronous serial interface for interfacing to a microcomputer, and a 68/80-type 8-bit or 4-bit bus interface. Access to on-chip registers and RAM can be performed by continuous high-speed writing, independently of the internal operating clock frequency, enabling adequately fast data transfer to be achieved even over a serial interface. In addition, built-in key-scan and port control functions enable the entire operating panel, including the liquid crystal display and key matrix, to be controlled via three serial interfaces. This makes it possible to use fewer parts and to cut the number of microcomputer I/O ports by more than 20, for example, resulting in lower system size, weight, power consumption, and costs.

Supported mounting methods are COG mounting, in which the device is directly mounted face-down on the LCD glass, COF mounting, in which the device is mounted face-down on a flexible film substrate, and TCP mounting, in which the device is connected to the LCD glass via a heatseal. To minimize the mounting glass area in COG mounting, a slim chip shape is used, with a width of only 2.78 mm.

Hitachi plans to expand the product lineup in the future, based on the HD 66728, to provide support for even larger display sizes.

Hitachi, Ltd., headquartered in Tokyo, Japan, is one of the world's leading global electronics companies, with fiscal 1997 (ending March 31, 1998) consolidated sales of 8,417 billion yen (63.8 billion dollars*). The company manufactures and markets a wide range of products, including computers, semiconductors, consumer products and power and industrial equipment. For more information on Hitachi, Ltd., please visit Hitachi's Web site at http://www.hitachi.co.jp.

*At an exchange rate of 132 yen to the dollar.

Notes 1. Graphic display:
On-chip bit-mapped display RAM is provided, and the microcomputer can display arbitrary patterns such as kanji and game patterns by rewriting display data dot by dot.
2. Character display:
An on-chip character generator that generates font patterns is provided, and the microcomputer can easily display kana, alphanumeric, and other characters in the character generator simply by specifying one-byte character codes.
3. COG (Chip On Glass):
A mounting method in which a chip with a gold bump is directly mounted face-down on the LCD glass.
4. COF (Chip On Film):
A mounting method in which a chip with a gold bump is directly mounted face-down on a flexible film substrate.
5. TCP (Tape Carrier Package):
A package in which the chip is mounted on a thin-film tape. Ultra-thin type mounting is possible.

Typical Applications

  • Digital cellular systems (PDC, GSM, CDMA, etc.), PHS
  • Message pagers
  • Simple portable terminals (electronic wallets, GPS terminals, POS terminals, etc.)

Prices in Japan (For Reference Only)

Product Code Display Size Shipment Form Mounting Form Sample Price (Yen)
HCD66728BP 112 x 80 dot Chip with gold bump COG, COF 600
HD66728TB0 Straight TCP TCP 900

[Supplementary Information]

Specifications
Item Specifications
Graphic display size 112 x 80 dots
Character display characters 10 lines x 16 digits (6 x 8-dot font)
Fonts (6 x 8 dots)
Built-in fixed fonts: 432
User-programmable fonts: 64
Display functions Graphics/character superimposed display
Vertical smooth scroll display
Screen top/bottom graphic icon display (fixed display)
Vertical double-size display (perpendicular enlarged display function)
Cursor display per display line
Blinking mark display support
Liquid crystal drive duty 1/32, 1/40, 1/48, 1/64, 1/72, 1/80 duty (programmable)
Liquid crystal drive bias 1/4 to 1/10 bias (programmable)
Liquid crystal drive step-up circuit output x3 to x5 output (programmable)
Power consumption control Sleep mode, standby mode functions
Variable liquid crystal drive duty/bias/voltage
Liquid crystal drive power supply on/off function
System interfaces Synchronous serial interface
68/ 80-type 4-bit bus interface
68/80-type 8-bit bus interface
Liquid crystal drive step-up circuit On-chip x3 to x5 step-up circuit
Liquid crystal drive power supply circuit On-chip liquid crystal drive level power supply op-amp
On-chip liquid crystal drive level bleeder resistance
On-chip electronic control for contrast adjustment
Key-scan functions 4 x 8 (32-key) matrix control
Key-scan interrupt generation
General output ports 3
Operating power supply voltage 1.8V to 5.5V
Liquid crystal drive voltage 5V to 15V
Total power consumption
(internal logic block + liquid crystal drive power supply block)
VCC = 3V, typ. conditions
Full-display: 420 microwatts
Partial display: 210 microwatts
No display (standby): 3 microwatts
Shipment forms Chip with gold bump (COG, COF)
Bent-lead TCP


WRITTEN BY Secretary's Office
All Rights Reserved, Copyright (C) 1998, Hitachi, Ltd.