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August 21, 1997

Hitachi Releases Single-Chip LCD Controller With On-Chip Bitmap RAM for Use in Portable Information Equipment

- Support for both the large screen size of 160 x 80 dots in a single chip for the first time in the industry and four-level gray scale display or four-color display with reflective color LCD panels -

Recently, information and communication infrastructures have been greatly improved and information can be acquired whenever and wherever desired. In this context, a wide range of portable information equipment has appeared on the market. There are now strong desires for the LCD displays used in these devices to be enlarged to display even more information and to support graphical display to improve visual impact. To respond to these needs and to achieve the miniaturization and reduced power consumption required in portable information equipment, single-chip implementations of LCD display systems and gray-scale and color display in the LCD controller driver circuit are required.

Hitachi is already mass producing the HD66410 LCD controller/driver with on-chip bitmap RAM. This device is designed for use in pagers and other multifunction portable telephone products and can drive a 128 x 33-dot monochrome LCD in a single chip. To further respond to these market needs, Hitachi has developed and is releasing the HD 66420. The HD 66420 includes 25.6K bits of bitmap RAM and an LCD drive power-supply circuit on chip. At the same time as supporting a 160 x 80-dot large screen display in a single chip for the first time in the industry, the HD66420 also achieves four-level gray scale display or four-color display with reflective color LCD panels.

Since the appearance of the displayed gray scale or colors differs depending on the characteristics of the LCD panel used, the HD66420 includes a 32-color palette and allows an arbitrary four colors to be selected for optimal four-color display on the LCD panel used. The HD66420 uses a variable pulse-width scheme to implement the gray scale/ color display, and thus achieves four- level/four-color display without flicker or smear. The HD 66420 can also drive reflective color LCDs that use the ECB (electrically controlled birefringence)(*2) technique to display four colors with the same drive circuit used for monochrome displays. It is also possible to implement 160 x 160-dot displays or 320 x 80-dot displays by connecting two chips in a master/slave(*3) configuration.

The HD66420 provides several power-saving features. One such feature is a partial display mode. This mode allows only an arbitrary 8 lines of the display to be driven, with the rest of the display turned off. This can be used to reduce power in standby mode. Another power-saving feature is the inclusion of the divider resistor, voltage follower, and electronic potentiometer circuit required for the LCD power-supply circuit. This allows application circuits to be implemented compactly, and the inclusion of the on-chip power-supply circuit can reduce the power consumption of the LCD system as a whole. The HD66420 is provided in a TCP (tape carrier package) format to support light-weight and compact implementation of LCD display systems.

Future developments in this area will include modified and enlarged display sizes and the incorporation of even more of the power-supply system components into the IC itself to even further reduce the number of external components required in the power-supply circuit.

- Note -
1. Bitmap RAM: Memory used to store the data bits corresponding to the image to be displayed.
2. ECB (electrically controlled birefringence): Refers to LCD panels that take advantage of the phenomenon that transmitted light that has been diffracted by liquid crystal molecules appears colored. Multi-color displays can be implemented since the color changes with the strength of the applied electric field. Currently, panels that support 4 or 5 colors have been produced commercially.
3. Master/slave connection: Refers to expanding the display size by using two or more ICs with one operating as the master and the other(s) operating as slave(s).

- Application Product Examples -
- Multifunction portable telephones
- Portable information equipment that includes communications functionality
- Bidirectional pagers

- Pricing in Japan -

Catalog No	Sample Price (yen)
HD66420TA0	1,400

- Features -
1. Large-screen drive circuit implemented in a single chip
The HD66420 achieves a 160 x 80-dot display in a single chip. Although the 128 x 33-dot HD66410 currently in volume production can display two lines with eight Japanese kanji characters, this new product can display five lines with ten characters.
2. Support for gray-scale or color display
Since the HD66420 supports arbitrary selection from a palette of 32 gray levels or colors, it supports optimal gray-level display and can drive the reflective color LCDs that require subtle voltage control. Also, the HD66420 uses a variable pulse-width scheme to implement the gray scale/color display, and thus achieves gray scale/color display without flicker or smear.
3. Support for partial display
As a low-power mode, the HD66420 supports a mode in which only 8 lines at an arbitrary position are displayed. This mode achieves reduced power consumption during standby by operating the LCD drive outputs from only the logic operating power supply, which makes the high voltage used for LCD drive unnecessary.

- Specifications -

Item		Specification
Internal RAM capacity		25.6K bits (160 x 80 x 2)
Number of LCD drive circuits	Segment outputs	160 outputs
	Common outputs	80 outputs
Color/gray-scale display		Simultaneous display of four colors /gray levels from a palette of 32 levels.
CPU interface		8-bit parallel 8086-compatible interface
Display duty		1/8, 1/32, 1/64, 1/80
Display control functions		Display on/off, vertical scroll, blinking, reverse video, partial display
Oscillator circuit		RC oscillator (Only requires an external resistor.)
Power-supply circuit		Bleeder resistor, voltage follower,electronic potentiometer
Power-supply voltage	VCC	1.8 V to 3.6 V
	VLCD	6 V to 13 V
Package		TCP

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