TW9903 データシートの表示（PDF） - Unspecified

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TW9903

Multi-standard Video Decoder With High Quality Down Scaler

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TW9903

Overview

Techwell’s TW9903 is a high quality NTSC/PAL/SECAM video decoder that is designed for

multimedia applications. It uses the mixed-signal 3.3V CMOS technology to provide a low-power

integrated solution.

The TW9903 analog front-end is equipped with three separate analog channels that enable it to

accept two possible analog video signal standards: composite or S-video. All channels include an

analog multiplexer (MUX) for maximum flexibility in software controlled input selection. It is possible

to connect up to four composite inputs at one time and allow the software to switch between them.

Alternatively several combinations of composite inputs and S-Video component inputs may be

switched under software control. (Four input channels of any format can be accommodated with

but there is a maximum of 2 S-Video inputs and 2 component inputs.)

The front-end contains all the necessary circuits to simplify the system design. AGC and clamping

circuits, and three 8-bit analog-to-digital converters (ADCs) convert inputs into digital signals for

processing.

The TW9903 uses proprietary adaptive comb filter for chroma and luma separation to achi eve high

video quality. The image enhancement uses nonlinear methods to enhance picture sharpness

with little overshoot.

The advanced synchronization processing can produce stable pictures for non-standard signal

such as those produced by VCR during fast forward, rewind or pause.

The high quality scaler uses multi-tap poly-phase decimation filter to reduce aliasing effects. It can

be programmed to scale-down the output picture to an arbitrary ratio with cropping.

The TW9903 supports flexible pixel int erface. It outputs YCbCr (4:2:2) data stream over 8-bit or

16-bit data path. The output is VMI 1.4 compatible.

A 2-wire serial MPU interface is used to simplify system integration. All the functions can be

controlled through this interface.

Analog Front-end

The analog front-end converts analog video signals to the required digital format. There are three

analog channels with clamping circuits and ADCs. The Y channel has 4-input multiplexer, and a

variable gain amplifier for automatic gain control (AGC). tIs four inputs are identified as MUX0,

MUX1, MUX2 and MUX3. The C_Pb channel has 2-input multiplexer. Its two inputs are identified

as C_PbIn0 and C_PbIn1. The C_Pb channel is internally clamped to the zero level of the bipolar

input source when enabled.

Video Source Selection

All analog signals should be AC-coupled to these inputs.

The Y channel analog multiplexer selects one of the four inputs MUX[0-3]. MUX[0-3] can be

connected to composite video inputs or the Y signal of an S-Video or component input. When

decoding a S-Video input, the Y signal should connect to one of the MUX inputs and the C signal

to C_PbIn0 or C_PbIn1.

TECHWELL, INC.

5

REV. 0.92 ( B )

06/02/2002

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