Integrated circuit for driving liquid crystal

A liquid crystal driving integrated circuit for generating a liquid crystal driving voltage that drives a liquid crystal panel to present a display from respective connection points of a plurality of serially connected resistor elements forming a first resistor, wherein a reference voltage applied to one end of said first resistor is variable so as to adjust display contrast of said liquid crystal panel, said circuit comprising:

• a second resistor formed by a plurality of serially connected resistor elements and connected to a power supply;
• a reference voltage generation circuit having a selection circuit for deriving one of voltages at respective connection points of said plurality of serially connected resistor elements forming said second resistor, and generating said reference voltage based on an output of said selection circuit;
• a first switch circuit (TG11) for selectively connecting said one end of said first resistor with the power supply or said reference voltage generation circuit;
• a second switch circuit (TG12) for connecting or disconnecting said second resistor with or from the power supply;
• and
• a circuit for enabling or disabling operation of said reference voltage generation circuit;
• wherein
• said first switch circuit is turned off and said second switch circuit is turned on when said reference voltage generation circuit is to be operated, and said first switch circuit is turned on and said second switch circuit is turned off when said reference voltage generation circuit is to be turned off.

A liquid crystal driving integrated circuit including a first resistor formed by a plurality of serially connected resistor elements, and generating a liquid crystal driving voltage for driving a liquid crystal panel to present a display from at least one of connection points of the serially connected resistor elements forming said first resistor, wherein a reference voltage applied to one end of said first resistor is changed to adjust display contrast of said liquid crystal panel, said circuit comprising:

• a second resistor formed by a plurality of serially connected resistor elements and having one end connected to a power supply;
• a reference voltage generation circuit for selecting a voltage at one of ends of the plurality of serially connected resistor elements forming said second resistor, wherein said reference voltage generation circuit including a selection circuit for selecting a voltage at one of the ends of said plurality of serially connected resistor elements forming said second resistor, and generating said reference voltage based on the selected voltage;
• and
• a control circuit for controlling the selection of the voltage by said reference voltage generation circuit based on control data applied from an external source, said control circuit including:
• a data holding circuit for holding control data, said control data including an instruction code and a selection code, applied from an external source to control said selection circuit, said data holding circuit including
• a shift register (13) for holding a bit string representing said control data;
• and
• a selection code extracting circuit for extracting said selection code from said shift register based on said instruction code and supplying the extracted code to said decoding circuit;
• and
• a decoding circuit (19) for decoding said control data held in said data holding circuit and generating a control signal to operate said selection circuit.