AN3114 datasheet(6/43 Pages) STMICROELECTRONICS

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LCD solution

AN3114

6/43

Doc ID 16829 Rev 3

LCD solution

1.1

Definitions

●

LCD (liquid crystal display): a passive display panel with terminals driving LCD

segments.

●

LCD segment (Pixel[i][j]): the smallest viewing element (a single bar or dot that is used

to help create a character on an LCD display)

●

Segment line (SEG[j]): segment terminal

●

Common (COM[i]): electrical connection terminal connected to several LCD segments

(denotes how many LCD segments (pixels) are connected to a segment line)

●

Duty ratio: number defined as 1 / (number of common terminals on an LCD display)

●

Bias: indicates the number of voltage levels used when driving an LCD. It is defined as

1 / (number of voltage levels used driving a LCD display - 1)

●

Von: the RMS voltage applied to the LCD segment that creates an ON pixel which is

typically at 90% of the contrast level

●

Vth (LCD threshold voltage): the RMS voltage across an LCD pixel when contrast

reaches a 10% level

●

Voff: the RMS voltage across an LCD pixel when contrast reaches a 0% level

●

Frame: one period of the waveforms written to a segment line

●

Frame rate: the number of frames per second, that is, the number of times the LCD

segments are energized per second

●

Boost circuit: contrast controller circuit

1.2

LCD principle

Figure 1.

LCD principle

An LCD panel is composed of many layers. A liquid crystal is filled between two of them

(glass plates), that are separated by thin spacers coated with transparent electrodes which

contain orientation layers.

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