Datasheet

POLARIZER
BOTTOM ITO
PLATE
TOP ITO
PLATE
POLARIZER
TRANSMITTED LIGHT
LIGHT SOURCE
GLASS
SUBSTRATE
LIQUID CRYSTAL
MATERIAL
GLASS
SUBSTRATE
V
PIXEL
± POLARITY
LM6588
SNOSA77D –MAY 2003–REVISED MARCH 2013 www.ti.com
The LM6588 meets these requirements. It has a rail-to-rail input and output, typical gain bandwidth and slew rate
of 15MHz and 15V/μs, and it can supply up to 200mA of output current. The following sections will describe the
operation of V
COM
Drivers, Gamma Buffers, and Panel Repair Buffers, showing how the LM6588 is well suited for
each of these functions.
BRIEF OVERVIEW OF TFT DISPLAY
To better understand these op amp applications, let’s first review a few basic concepts of how a TFT display
operates. Figure 25 is a simplified illustration of an LCD pixel. The top and bottom plates of each pixel consist of
Indium-Tin oxide (ITO), which is a transparent, electrically conductive material. ITO lies on the inner surfaces of
two glass substrates that are the front and back glass panels of a TFT display. Sandwiched between the two ITO
plates is an insulating material (liquid crystal) that alters the polarization of light to a lesser a greater amount,
depending on how much voltage (V
PIXEL
) is applied across the two plates. Polarizers are placed on the outer
surfaces of the two glass substrates, which in combination with the liquid crystal create a variable light filter that
modulates light transmitted from the back to the front of a display. A pixel’s bottom plate lies on the backside of a
display where a light source is applied, and the top plate lies on the front, facing the viewer. On a Twisted
Neumatic (TN) display, which is typical of most TFT displays, a pixel transmits the greatest amount of light when
V
PIXEL
is less ±0.5V, and it becomes less transparent as this voltage increases with either a positive or negative
polarity. In short, an LCD pixel can be thought of as a capacitor, through which, a controlled amount of light is
transmitted by varying V
PIXEL
.
Figure 25. Individual LCD Pixel
14 Submit Documentation Feedback Copyright © 2003–2013, Texas Instruments Incorporated
Product Folder Links: LM6588