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TDA3566 датащи(PDF) 6 Page - NXP Semiconductors |
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TDA3566 датащи(HTML) 6 Page - NXP Semiconductors |
6 / 24 page February 1994 6 Philips Semiconductors Product specification PAL/NTSC decoder TDA3566A The time constant of the saturation control (pin 5) provides a delayed switch-on after killing. Adjustment of the oscillator is achieved by variation of the burst phase detector load resistance between pins 24 and 25 (see Fig.8). With this application the trimmer capacitor in series with the 8.8 MHz crystal (pin 26) can be replaced by a fixed value capacitor to compensate for unbalance of the phase detector. Demodulator The (R −Y) and (B−Y) demodulators are driven by the colour difference signals from the delay-line matrix circuit and the reference signals from the 8.8 MHz divider circuit. The (R −Y) reference signal is fed via the PAL-switch. The output signals are fed to the R and B matrix circuits and to the (G −Y) matrix to provide the (G −Y) signal which is applied to the G-matrix. The demodulation circuits are killed and blanked by by-passing the input signals. NTSC mode The NTSC mode is switched on when the voltage at the burst phase detector outputs (pins 24 and 25) is adjusted below 9 V. To ensure reliable application the phase detector load resistors are external. When the TDA3566A is used only for PAL these two 33 k Ω resistors must be connected to +12 V (see Fig.8). For PAL/NTSC application the value of each resistor must be reduced to 20 k Ω (with a tolerance of 1%) and connected to the slider of a potentiometer (see Fig.9). The switching transistor brings the voltage at pins 24 and 25 below 9 V which switches the circuit tot the NTSC mode. The position of the PAL flip-flop ensures that the correct phase of the (R −Y) reference signal is supplied to the (R −Y) demodulator. The drive to the H/2 detector is now provided by the (B −Y) reference signal. In the PAL mode it is driven by the (R −Y) reference signal. Hue control is realized by changing the phase of the reference drive to the burst phase detector. This is achieved by varying the voltage at pins 24 and 25 between 7.0 V and 8.5 V, nominal position 7.65 V. The hue control characteristic is shown in Fig.6. RGB matrix and amplifiers The three matrix and amplifier circuits are identical and only one circuit will be described. The luminance and the colour difference signals are added in the matrix circuit to obtain the colour signal, which is then fed to the contrast control stage. The contrast control voltage is supplied to pin 6 (high-input impedance). The control range is +5 dB to −11.5 dB nominal. The relationship between the control voltage and the gain is linear (see Fig.3). During the 3-line period after blanking a pulse is inserted at the output of the contrast control stage. The amplitude of this pulse is varied by a control voltage at pin 11. This applies a variable offset to the normal black level, thus providing brightness control. The brightness control range is 1 V to 3.6 V. While this offset level is present, the black-current input impedance (pin 18) is high and the internal clamp circuit is activated. The clamp circuit then compares the reference voltage at pin 19 with the voltage developed across the external resistor network RA and RB (pin 18) which is provided by picture tube beam current. The output of the comparator is stored in capacitors connected from pins 10, 20 and 21 to ground which controls the black level at the output. The reference voltage is composed by the resistor divider network and the leakage current of the picture tube into this bleeder. During vertical blanking, this voltage is stored in the capacitor connected to pin 19, which ensures that the leakage current of the CRT does not influence the black current measurement. The RGB output signals can never exceed a level of 10.6 V. When the signal tends to exceed this level the output signal is clipped. The black level at the outputs (pins 13, 15 and 17) will be approximately 3 V. This level depends on the spread of the guns of the picture tube. If a beam current stabilizer is not used it is possible to stabilize the black levels at the outputs, which in this application must be connected to the black current measuring input (pin 18) via a resistor network. |
Аналогичный номер детали - TDA3566 |
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Аналогичное описание - TDA3566 |
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