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TDA9815 Datasheet(PDF) 7 Page - NXP Semiconductors |
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TDA9815 Datasheet(HTML) 7 Page - NXP Semiconductors |
7 / 40 page 1998 Feb 11 7 Philips Semiconductors Product specification Multistandard/MAC VIF-PLL with QSS-IF and dual FM-PLL/AM demodulator TDA9815 The demodulator output signal is fed via an integrated low-pass filter for attenuation of the carrier harmonics to the video amplifier. The video amplifier is realized by an operational amplifier with internal feedback and high bandwidth. A low-pass filter is integrated to achieve an attenuation of the carrier harmonics for B/G and L standard. The standard dependent level shift in this stage delivers the same sync level for positive and negative modulation. The video output signal is 1 V (p-p) for nominal vision IF modulation. Video buffer For an easy adaption of the sound traps an operational amplifier with internal feedback is used in the event of B/G and L standard. This amplifier is featured with a high bandwidth and 7 dB gain. The input impedance is adapted for operating in combination with ceramic sound traps. The output stage delivers a nominal 2 V (p-p) positive video signal. Noise clipping is provided. For MAC standard a second buffer amplifier with 6 dB gain is used. This buffer amplifier is selected by the standard switch. SIF amplifier and AGC The sound IF amplifier consists of two AC-coupled differential amplifier stages. Each differential stage comprises a controlled feedback network provided by emitter degeneration. The SIF AGC detector is related to the SIF input signals (average level of AM or FM carriers) and controls the SIF amplifier to provide a constant SIF signal to the AM demodulator and single reference QSS mixer. The SIF AGC reaction time is set to ‘slow’ for nominal video conditions. But with a decreasing VIF amplitude step the SIF AGC is set to ‘fast’ mode controlled by the VIF-AGC detector. In FM mode this reaction time is also set to ‘fast’ controlled by the standard switch. Single reference QSS mixer The single reference QSS mixer is realized by a multiplier. The SIF amplifier output signal is fed to the single reference QSS mixer and converted to intercarrier frequency by the regenerated picture carrier (VCO). The mixer output signal is fed via a high-pass for attenuation of the video signal components to the output pin 20. With this system a high performance hi-fi stereo sound processing can be achieved. AM demodulator The AM demodulator is realized by a multiplier. The modulated SIF amplifier output signal is multiplied in phase with the limited (AM is removed) SIF amplifier output signal. The demodulator output signal is fed via an integrated low-pass filter for attenuation of the carrier harmonics to the AF amplifier. FM-PLL demodulator Each FM-PLL demodulator consists of a limiter, an FM-PLL and an AF amplifier. The limiter provides the amplification and limitation of the FM sound intercarrier signal before demodulation. The result is high sensitivity and AM suppression. The amplifier consists of 7 stages which are internally AC-coupled in order to minimize the DC offset and to save pins for DC decoupling. At the input of one limiter a signal switch is available for selecting one of the two intercarrier signals. Controlled by the voltage at pin 11, either the input pin 17 or pin 18 is active for handling different intercarrier frequencies. The other limiter is extended with an additional level detector consisting of a rectifier and a comparator. By means of this the AF2 signal is set to mute and the PLL VCO is switched off, if the intercarrier signal at pin 16 is below 1 mV (RMS) in order to avoid false identification of a stereo decoder. Note that noise at pin 16 disables the mute state (at low SIF input signal), but this will not lead to false identification. This ‘auto-mute’ function can be disabled by connecting a 5.6 k Ω resistor from pin 16 to V P (see Fig.13). Furthermore the AF output signals can be muted by connecting a resistor between the limiter inputs pin 16 or pin 17 and ground. The FM-PLL consists of an integrated relaxation oscillator, an integrated loop filter and a phase detector. The oscillator is locked to the FM intercarrier signal, output from the limiter. As a result of locking, the oscillator frequency tracks with the modulation of the input signal and the oscillator control voltage is superimposed by the AF voltage. The FM-PLL operates as an FM-demodulator. |
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