The present invention relates to a semiconductor integrated circuit device for driving liquid crystal (a liquid crystal control driver IC) that drives a liquid crystal display panel and, more particularly, to a technique effectively used for a liquid crystal control driver IC having means for setting characteristics and specifications of a liquid crystal display panel used in a non-volatile manner.
In recent years, as displays of portable electronic devices such as cellular phones and PDA (Personal Digital Assistants), generally, dot-matrix-type liquid crystal panels in each of which a plurality of display pixels are arranged two-dimensionally in a matrix are used. In a device, a display controller (liquid crystal controller IC) formed in a semiconductor integrated circuit for controlling display of the liquid crystal panel and a driver circuit for driving the liquid crystal panel or a liquid crystal display driver (liquid crystal control driver IC) having therein such a driver circuit are mounted.
The specifications such as gamma characteristic, drive voltage, operation clock frequency, and the like of a liquid crystal display vary according to kinds of liquid crystals used and driving methods, and the characteristics vary due to manufacture variations. Manufacturers providing liquid crystal display drivers construct liquid crystal display drivers so as to be adapted to liquid crystal displays of different specifications and liquid crystal displays having manufacture variations. The manufactures are devising methods of increasing versatility of the drivers and decreasing the manufacture cost.
Hitherto, as a measure for enabling liquid crystal displays of different specifications to be driven, a method is practically used in which a register is provided in a liquid crystal display driver. Simultaneously, a nonvolatile memory such as an EPROM is provided on the outside. For initial setting or the like at power-on, setting information such as drive conditions is transferred from the nonvolatile memory to the register on the inside. Another method has been also proposed. A setting circuit having a fuse and the like is provided in a liquid crystal display driver. On determination of a liquid crystal display applied, setting is performed by disconnecting a fuse in accordance with the specifications of the liquid crystal display. An invention of adjusting operation characteristics of a liquid crystal driver by using fuses is disclosed in, for example, Japanese Unexamined Patent Publication No. 2000-148064.
USPTO Backgrounds
USPTO Backgrounds