COLUMN DRIVER FOR A DISPLAY

摘要

A column driver (110) for a matrix addressed display such as a liquid crystal display (LCD) is disclosed. The column driver (110) accepts 10-bit inputs, provides 1024 distinct output levels, and is compatible with digital gamma correction by way of, for example, an EPROM lookup table. A complete column driver (110) includes a group of chips (CHIP1-CHIP5) which are serially interconnected and receive all the external signals applied in parallel. Only one chip (210) is made active at any instant of time, in order to save power. In each IC (210) selective polarity inversion of the 10-bit data is carried out before feeding it to a switched capacitor digital to analog converter (CAPDAC) (224) which operates in either a high or low voltage range. All CAPDACs (224) are loaded simultaneously and present a precise output for approximately 95 % of each linetime. Each CAPDAC (224) output is connected to a buffer opamp (228) via two CMOS switches which cause the CAPDAC (224) to simultaneously yet transparently change range and allow the opamp buffer (228) to continue driving.