Datasheet

TVP5154A

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SLES214C–DECEMBER 2007–REVISED SEPTEMBER 2010

3 Functional Description

3.1 Analog Front End

Each channel of the TVP5154A decoder has an analog input channel that accepts two video inputs, which

should be ac coupled through 0.1-µF capacitors. The decoder supports a maximum input voltage range of

0.75 V; therefore, an attenuation of one-half is needed for standard input signals with a peak-to-peak

variation of 1.5 V. The maximum parallel termination before the input to the device is 75 Ω. See the

schematic in Section 10 for recommended configuration. The two analog input ports can be connected as

follows:

• Two selectable composite video inputs or

• One S-video input

An internal clamping circuit restores the ac-coupled video signal to a fixed dc level.

The programmable gain amplifier (PGA) and the automatic gain control (AGC) circuit work together to

ensure that the input signal is amplified or attenuated correctly, ensuring the proper input range for the

ADC.

When switching CVBS inputs from one input to the other, the AGC settings are internally stored and the

previous settings for the new input are restored. This eliminates flashes and dark frames associated with

switching between inputs that have different signal amplitudes.

The ADC has nine bits of resolution and runs at a maximum speed of 27 MHz. The clock input for the

ADC comes from the PLL.

3.2 Composite Processing Block Diagram

The composite processing block processes NTSC/PAL/SECAM signals into the YCbCr color space.

Figure 2-1 shows the basic architecture of this processing block.

Figure 2-1 shows the luminance/chrominance (Y/C) separation process in the TVP5154A decoders. The

composite video is multiplied by sub-carrier signals in the quadrature modulator to generate the color

difference signals Cb and Cr. Cb and Cr are then low pass (LP) filtered to achieve the desired bandwidth

and to reduce crosstalk.

An adaptive 4-line comb filter separates CbCr from Y. Chroma is remodulated through another quadrature

modulator and subtracted from the line-delayed composite video to generate luma. Contrast, brightness,

hue, saturation, and sharpness (using the peaking filter) are programmable via I

The Y/C separation is bypassed for S-video input. For S-video, the remodulation path is disabled.

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