LARGE_LCD_DISPLAY_BUFFERING_DRIVER

Published:2009/6/15 23:30:00 Author:May | From:SeekIC

Large LCD devices of 1 or more exhibit a large driving capacitance to the driver circuits. To solve this problem, the drive cir-cuit shown (see the figure) introduces a buffer amplifier for each of the three common lines. Each amplifier can be programmed independently for a quiescent current of 10, 100, or 1000μA. In this application, the bias network applies a voltage that sets the three quiescent currents to 100μA.The display driver and triple op amp operate between 5 V and ground, and the COM signals range from 5 V to ≈1 V. To en-sure that these signals remain within the amplifiers' common-mode range, the signals are attenuated by one-half and the buffers operate at a gain of two. The circuit drives eight 1-inch displays, and is suitable for ambient temperature variations of 15°F or Iess.At the highest expected temperature, R1 should be adjusted so that no off segments are visible.



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