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                      | HITACHI HOME | UP | SEARCH | HITACHI

                      News Release

                      October 15, 1998

                      Hitachi Releases Low-Power Color Liquid Crystal Driver Chip-Set for PDAs

                      — Low-power-consumption drive method cuts power consumption by 50% —

                      Hitachi, Ltd. (NYSE:HIT) today announced a low-power-consumption liquid crystal driver 
                      chip-set, comprising the HD66136 and HD66137, which is ideal for use with liquid crystal 
                      displays in portable information devices such as PDAs (personal digital assistants).  Sample 
                      shipments will begin in December 1998 in Japan.
                      
                      LCDs, with their features of lightness, thinness, and low power consumption, are widely 
                      used as display systems in portable information devices such as PDAs.  With the increasing 
                      popularity of portable telephones and the Internet, there is a demand for higher quality 
                      displays in portable information devices, including larger screen size and color capability, as 
                      well as ultra-low power consumption allowing use of these devices for periods exceeding 20 
                      hours.
                      
                      With a conventional LCD panel configuration, improving picture quality by increasing the 
                      display area, providing color capability, and so forth, means increasing the number of drive 
                      elements, and thus also the power consumption.  While various techniques have already been 
                      devised to reduce the power consumption of the logic circuits within LSIs, it also became 
                      necessary to devise a drive method that reduces the charge/discharge power of the liquid 
                      crystal panel, which is driven at a high voltage.
                      
                      With the conventional liquid crystal drive method, liquid crystal elements are charged and 
                      discharged using the same high voltage (of around 20 V or so) for both segment and 
                      common drivers.  Usually, the segment drivers switch the output potential at high speed, and 
                      a large number are used to provide color capability. The common drivers, on the other hand, 
                      operate at low speed, performing only line scanning pulse drive, and only one or two are 
                      used in the system configuration.
                      
                      By using a new drive method that employs a low drive voltage of 3 to 6 V for the large 
                      number of high-speed segment drivers, it is possible to reduce the liquid crystal panel 
                      charge/discharge power and greatly decrease the overall power consumption of large, color 
                      LCDs, something that has previously been difficult to achieve.
                      
                      In developing the HD66136/HD66137 liquid crystal chip-set for medium-sized color LCDs 
                      of 320×240 to 640×240 dots, ideal for color PDA use, Hitachi has employed a new liquid 
                      crystal drive method to achieve lower power consumption.
                      
                      In addition to cutting power consumption, the new liquid crystal drive method used in this 
                      chip-set also provides improved image quality by reducing the amplitude of the liquid crystal 
                      drive waveform, thus minimizing drive waveform distortion and preventing a decrease in 
                      contrast.
                      
                      The HD66136/HD66137 chip-set is of the simple driver type, and has the same drivers and 
                      interface as the conventional drive method, allowing a conventional liquid crystal module to 
                      be directly replaced by a module using this chip-set.  This alone will result in an 
                      approximately 50% reduction in overall display system power consumption (in the case of a 
                      640×240-dot color display).
                      
                      The HD66136 segment driver chip can switch between 400 and 384 liquid crystal drive 
                      outputs, for compatibility with a wide variety of liquid crystal panels, and when used in 
                      combination with the HD66137 common driver chip, can implement a 640×240-dot color 
                      display with a 5-chip/1-chip configuration, enabling the number of parts to be significantly 
                      reduced.
                      
                      The HD66137 common driver chip incorporates part of the liquid crystal drive power supply 
                      circuitry, enabling a conventional power supply circuit to be used with the new drive 
                      method.  In addition, signals for liquid crystal drive output alternation can be set for any 
                      number of lines, to suit the frequency characteristics of the liquid crystal used.
                      
                      The packages used are TCPs (tape carrier packages), for lightweight, compact liquid crystal 
                      displays with a small mounting area.  Future development plans include models offering an 
                      even greater reduction in power consumption.
                      
                      < Applications >
                      PDAs
                      Sub-notebook PCs
                      
                      < Prices in Japan >
                      
                      Product CodeSample Price (Yen)
                      HD66136TA0500
                      HD66137TA0750
                      
                      < Features >
                      1. Low power consumption
                      Use of a new low-voltage liquid crystal drive method has enabled the segment driver liquid 
                      crystal drive voltage to be reduced to 3 to 6 V, reducing power consumption to 50% that of 
                      the conventional method.
                      2. Improved display quality
                      Use of a low-voltage liquid crystal drive method has improved the display quality by 
                      reducing crosstalk, etc.
                      3. Large number of outputs
                      An increased number of outputs enables the number of parts to be reduced.
                      4. Part of power supply circuitry provided on-chip (HD66137)
                      A conventional power supply circuit can be used with the new liquid crystal drive method.
                      
                      
                      
                      < Specifications >
                      HD66136 (segment driver chip)
                      
                      
                      ItemSpecification
                      FunctionDot matrix liquid crystal drive segment driver
                      Liquid crystal drive outputsSwitchable: 400/384 outputs
                      Data transfer frequency33MHz/3 V
                      40MHz/5 V
                      Operating voltage2.7 V to 5.5 V
                      Liquid crystal drive power supply voltage3.5 V to 5.5 V
                      Package438-pin TCP

                      
                      HD66137 (common driver chip)
                      
                      
                      ItemSpecification
                      FunctionDot matrix liquid crystal drive common driver
                      Liquid crystal drive outputsSwitchable: 240/200/160 outputs
                      Other functionsPart of power supply circuitry on-chip, on-chip alternation signal generation circuit
                      Operating voltage2.7 V to 5.5 V
                      Liquid crystal drive power supply voltage20 V to 43 V
                      Package273-pin TCP


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

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