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TDA4504B Scheda tecnica(PDF) 7 Page - NXP Semiconductors |
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TDA4504B Scheda tecnica(HTML) 7 Page - NXP Semiconductors |
7 / 26 page February 1992 7 Philips Semiconductors Product specification Small signal combination for multistandard colour TV TDA4504B AGC circuit For signals employing negative modulation the AGC detector operates on peak sync level but upon peak white content with those having positive modulation. Selection is facilitated by the system switch (pin 32): The AGC detector currents are: With a 6.8 µF AGC capacitor, the video tilt will be < 10% for positively modulated signals and < 2% for negative modulation. To obtain a rapid AGC action when executing a search tuning operation with the circuit set for peak white AGC, the charge current is held at 55 µA until the detection of a transmitted signal. The transmitter identification A mute signal is generated to disable the audio preamplifier of an audio demodulator during the absence of a transmission signal. When the video switch is in the internal mode, the identification of a transmitted signal is derived from the coincidence detector. In the external mode the IF part of the circuit has its own identification system. The system relies upon the detection of sync. pulses on the incoming IF signal. The separated horizontal sync pulse charges the capacitor on pin 25 which drives the mute output (pin 14). The connection of a 1 M Ω resistor between pin 25 and VCC results in the mute information being overruled by the 50/60 Hz information derived from the internal vertical divider section (see 50/60 Hz truth table). MUTE Truth Table: pin 32 HIGH/open: positive modulation pin 32 LOW: negative modulation positive modulation negative modulation charge 1 µA55 µA discharge 3 mA 1.5 mA Input signal Pins 9 and 10 50 Hz 60 Hz none 50/60 Hz 50/60 Hz 50/60 Hz none pin 25 9.5 V 9.5 V 0.3 V 9.5 V 9.5 V 9.5 V 0.3 V pin 28 50 Hz 60 Hz none 50 Hz 60 Hz none 50/60 Hz pin 18 LOW LOW LOW/ HIGH HIGH HIGH HIGH HIGH pin 14 12 V 9 V 0.3 V 12 V 9 V 12 V 0.3 V |
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