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TDA3567

NTSC decoder

Philips Electronics 

Philips Semiconductors

NTSC decoder

Product specification

TDA3567

In these equations (R-Y)IN and (B-Y)IN indicate the colour difference signal amplitudes, when the chrominance signal is

demodulated with a phase difference between the R-Y and B-Y demodulator of 90° and a gain ratio B-Y/R-Y = 1,78.

RGB matrix circuit and amplifiers

The three matrix and amplifier circuits are identical. The luminance signal and the colour difference signals are added in

the matrix circuit to obtain the colour signal.

Output signals are 5 V (peak-to-peak) (black-white) for the following nominal input signals and control settings.

• Luminance 450 mV (peak-to-peak)

• Chrominance 550 mV (peak-to-peak) (burst-to-chrominance ratio of the input 1 : 2.2)

• Contrast −3 dB (maximum)

• Saturation −10 dB (maximum)

The maximum available output voltage is approximately 7 V (peak-to-peak). The black level of the red channel is

compared with a variable external reference level (pin 9), which provides the brightness control. The control loop is

closed via the luminance input.

The luminance input is varied to control the black level control, therefore the green and blue outputs will follow any

variation of the red output. The output of the black control can be varied between 2 V to 4 V. The corresponding

brightness control voltage is shown in Fig.4.

If the output signal surpasses the level of 9 V the peak-white limiter circuit becomes active and reduces the output signal

via the contrast control.

Blanking of RGB signals

A slicing level of about 1,5 V is used for this blanking function, so that the wide part of the sandcastle pulse is separated

from the rest of the pulse. During blanking a level of + 2 V is available at the output.

June 1986

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