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April 9, 1997
Hitachi, Ltd. announces the release of two LCD driver chip sets offering a 30% reduction in power consumption compared with previous Hitachi products, for use with the liquid crystal displays of hand-held PCs, PDAs (personal digital assistants), and similar portable information devices. Sample shipments will begin in May 1997 in Japan. These two new sets comprise the HD66522 and HD66523, designed for low power consumption and also incorporating frame memory to reduce the number of system components, and the multi-output HD66130 and HD66131 that enable a 640 x 480-dot LCD to be driven with a total of four chips.With such features as lightness, thinness, and low power consumption, LCDs are widely used as the display system for portable information devices. To make such devices really effective, there is a need for larger screen sizes as well as high speed and long operating periods made possible by low power consumption. The features demanded of an LCD driver are thus the ability to handle larger screen sizes together with ever lower power consumption.
To respond to these needs, Hitachi currently offers the HD 66120T/HD66115T LCD driver chip set. Hitachi is releasing the two new LCD driver chip sets, the HD66522/HD66523 and HD 66130/HD66131, in which power consumption has been cut by 30% compared with previous Hitachi products by changing the LCD drive method, for medium-sized LCDs from 320 x 240 to 640 x 480 dots. The lower power consumption also enables better display quality to be achieved.
The HD66522 (segment driver(*1))/HD66523 (common driver(*2)) chip set has built-in frame memory which eliminates the need for controller memory for display data transfer, enabling the number of system components to be reduced while achieving low power consumption. Changing the drive method has reduced power consumption by 30% compared with previous Hitachi products with built-in frame memory, and by approximately 70% in terms of the overall display system compared with products without built-in frame memory.
The HD66522 segment driver includes a gradation palette that allows four gradations to be selected from a total of 32, for a gradation display appropriate to the LCD used. A 32-gradation setting is also possible, allowing driving of reflective color LCDs that require precise voltage regulation. The HD66130/HD66131 chip set is a multi-output driver. The HD 66130 segment driver has 320 LCD drive outputs, providing drive capability, in combination with the HD66131 common driver, of a 320 x 240-dot LCD using just two chips (one of each), or a 640 x 480-dot LCD using just four chips (two of each). The number of system components can thus be significantly reduced. The driver interface is the same as for the previous drive method, simplifying replacement of previous products. The use of TCPs (tape carrier packages) makes it possible to produce light, compact LCDs with a narrow frame.
Future development plans include increasing the number of display gradations and support for low-power-consumption transparent color displays as well as the reflective type.
Note
1. Segment driver: Also referred to as the column driver or data driver. Normally installed at the top and bottom of an LCD, performing display data output.
2. Common driver: Also referred to as the row driver or line driver. Normally installed at the left or right of an LCD, performing line selection.Application Product Examples
- Portable information devices such as hand-held PCs and PDAs.
- High-end portable phones (models combined with information devices, etc.)Pricing in Japan
Product No Sample Price (yen) HD66522TA0 1,200 HD66523TA0 1,400 HD66130TA0 900 HD66131TA0 1,300 Features
1. Low power consumption
Use of an LCD drive method designed for low power consumption has enabled LCD driver power consumption to be reduced by 30% compared with previous LCD drivers.
2. Improved display quality
Effects of the lower power consumption include reduced waveform distortion, which results in improved LCD display quality.
3. Built-in gradation palette (HD66522)
The 32-gradation palette included in the HD66522 segment driver allows any desired gradations to be selected, enabling optimal gradation display to be achieved. This feature also makes it possible to drive reflective color LCDs that require precise voltage regulation.Detailed Description
These two chip sets employ a new LCD drive method in order to reduce power consumption with larger LCD screens. The drive method currently in general use requires a high voltage (of around 20 V) for both the segment and common driver. Since the power for discharging the LCD load accounts for a significant proportion of LCD power consumption, however much the power consumption of the LCD driver itself is reduced with this method, there is a limit in terms of the overall display system. With the LCD drive method used in the new chip sets, the segment driver uses 3 to 6 V, and the common driver 30 to 40 V. Although the common driver requires a higher voltage than with the previous method, a lower voltage can be used for the segment driver, of which many are used, reducing the LCD load discharge current which accounts for a large proportion of the power consumption. This has made it possible to achieve a 30% cut in overall LCD power consumption, an area in which reductions have been difficult to achieve with the previous drive method. The new method also features a smaller LCD drive output amplitude, resulting in lower waveform distortion, and any reduction in contrast has been suppressed, helping to improve display quality. The HD66522 segment driver has on-chip 76.8-kbit frame memory and uses a general-purpose SRAM interface, simplifying system configuration. The built-in gradation palette, which allows selection of four gradations from 32, makes it possible to implement a gradation display suited to the LCD used. A 32-gradation setting is also possible, allowing driving of reflective color LCDs that require precise voltage regulation. The HD66523 common driver has an on-chip oscillator and LCD drive timing signal generator, eliminating the need for a dedicated display controller, etc. It is also possible to set a vertical retrace line interval in which LCD drive outputs do not operate at all, and latching of tablet and other data susceptible to noise can be carried out during this interval. The HD66130 segment driver, with 320 outputs, and the HD66131 common driver, with 240 outputs, are multi-output products. The HD 66131 also allows the signals for AC conversion of LCD drive outputs to be set at any desired number of lines, to suit the frequency characteristics of the liquid crystal used.Specifications
HD66522 (segment driver)
Item Specification Function Segment driver with built-in frame memory On-chip RAM capacity 76.8 kbits (160 bits x 240 lines x 2 planes) LCD drive outputs 160 outputs Gradation display 4 gradations/32 gradations selectable CPU interface General-purpose SRAM interface Access time 120 ns/3 V (typ) Power consumption 0.5 mW (during display) Operating supply voltage 2.4 to 3.6 V LCD drive supply voltage 4 to 6 V Package 213-pin TCP HD66523 (common driver)
Item Specification Function Common driver with built-in LCD timing signal generator LCD drive outputs 240/200 outputs Oscillator Built-in oscillator using external C, R Duty setting 1/200, 1/240 duty Power consumption 0.8 mW Other functions Built-in display-off function, master/slave switching, vertical retrace line interval setting Operating supply voltage 2.4 to 3.6 V LCD drive supply voltage 30 to 40 V Package 273-pin TCP HD66130 (segment driver)
Item Specification Function Dot matrix LCD drive segment driver LCD drive outputs 320 outputs/240 outputs switchable Data transfer frequency 6.5 MHz/ 3 V8.0 MHz/ 5 V Power consumption 0.8 mW Operating voltage 2.5 to 5.5 V LCD drive supply voltage 2.6 to 5.5 V Package 346-pin TCP HD66131 (common driver)
Item Specification Function Dot matrix LCD drive common driver LCD drive outputs 240/200/160 outputs switchable Other functions Built-in display-off function, built-in AC conversion signal generator Power consumption 0.8 mW Operating voltage 2.5 to 5.5 V LCD drive supply voltage 20 to 43 V Package 268-pin TCP
