Block Diagram

Functional Description

GENERAL OVERVIEW

The FPD03784 is a low power, low EMI, 384 output column

driver with 64 gray level capability (6-bit). It provides direct

drive for TFT-LCD displays, eliminating the need for V

com

modulation. Direct drive significantly reduces system power

consumption and also reduces component count while pro-

viding superior image quality and cross-talk margin. The

FPD03784 utilizes National’s

Charge Conservation Technol-

ogy that recovers energy stored in the capacitance of the

column lines to reduce power consumption further.

The FPD03784 is designed for use in systems using dot

inversion as the method of polarity inversion. Column inver-

sion and N-line inversion are also supported. Other modes of

polarity inversion including line inversion and frame inversion

are not supported.

Digital video data inputs to the FPD03784 are received on

six, six bit wide busses (dual bank, RGB busses) using TTL

signaling. The digital video commands one of 64 gray level

voltages on each output. Output voltages are driven with

individual high drive, low offset, programmable-slew-rate,

operational amplifiers. Data loading and line buffering is

accomplished by means of an internal, bi-directional shift

register.

GAMMA CORRECTION

The FPD03784 is designed to offer compatibility with a wide

range of panel gamma characteristics. The output voltage

levels corresponding to each of the 64 gray level commands

can be externally adjusted to match the desired gamma

characteristics of the display by means of two internal

resistor-string DACs (RDACs). One RDAC provides the

high-polarity output voltages (voltages higher than V

the other provides the low-polarity output voltages (voltages

lower than V

The default RDAC resistance values have been carefully

designed to provide a smooth 2.2 gamma characteristic in a

twisted nematic (TN) display. This is especially useful for

monitor applications. Consequently, most application de-

signs will only need to provide references for each of the two

ends of the two RDACs (four gamma references). Additional,

intermediate taps to the RDAC are also provided for optional

customization of the display gamma for contrast control as

an example.

CHARGE CONSERVATION TECHNOLOGY

National Semiconductor’s proprietary charge conservation

technology

significantly

reduces

power

consumption.

Charge conservation works by briefly switching all of the

columns at the start of each line to a common node. This has

DS200152-6

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