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TDA9808 датащи(PDF) 6 Page - NXP Semiconductors |
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TDA9808 датащи(HTML) 6 Page - NXP Semiconductors |
6 / 36 page 1999 Jun 04 6 Philips Semiconductors Product specification Single standard VIF-PLL with QSS-IF and FM-PLL demodulator TDA9808 FUNCTIONAL DESCRIPTION The integrated circuit comprises the functional blocks as shown in Fig.1: 1. Vision IF amplifier and VIF AGC detector 2. Tuner AGC 3. Frequency Phase Locked Loop (FPLL) detector 4. Voltage Controlled Oscillator (VCO), Travelling Wave Divider (TWD) and AFC 5. Video demodulator and amplifier 6. SIF amplifier and SIF AGC 7. Single reference QSS mixer 8. FM-PLL demodulator 9. Audio Frequency (AF) signal processing 10. Internal voltage stabilizer. Vision IF amplifier and VIF AGC detector The vision IF amplifier consists of three AC-coupled differential amplifier stages. Each differential stage comprises a feedback network controlled by emitter degeneration. The AGC detector generates the required VIF gain control voltage for constant video output by charging/discharging the AGC capacitor. Therefore, for negative video modulation the synchronisation level of the video signal is detected. Tuner AGC The AGC capacitor voltage is converted to an internal IF control signal, and is fed to the tuner AGC to generate the tuner AGC output current at pin TAGC (open-collector output). The tuner AGC takeover point can be adjusted at pin TADJ. This allows to match the tuner to the SAW filter in order to achieve the optimum IF input level. Frequency Phase Locked Loop (FPLL) detector The VIF-amplifier output signal is fed into a frequency detector and into a phase detector via a limiting amplifier. During acquisition the frequency detector produces a DC current proportional to the frequency difference between the input and the VCO signal. After frequency lock-in the phase detector produces a DC current proportional to the phase difference between the VCO and the input signal. The DC current of either the frequency detector or the phase detector is converted to a DC voltage via the loop filter, which controls the VCO frequency. VCO, Travelling Wave Divider (TWD) and AFC The VCO operates with a resonance circuit (with L and C in parallel) at double the Picture Carrier (PC) frequency. The VCO is controlled by two integrated variable capacitors. The control voltage required to tune the VCO from its free-running frequency to double the PC frequency is generated by the frequency-phase detector of the FPLL and fed via the loop filter to the first variable capacitor. This control voltage is amplified and additionally converted into a current which represents the AFC output signal. At the centre frequency the AFC output current is equal to zero. The oscillator signal is divided-by-two with a TWD which generates two differential output signals with a 90 degree phase difference independent of the frequency. Video demodulator and amplifier The video demodulator is realized by a multiplier which is designed for low distortion and large bandwidth. The vision IF input signal is multiplied with the ‘in phase’ signal of the travelling wave divider output. The demodulator output signal is fed to the video amplifier via an integrated low-pass filter for attenuation of the carrier harmonics. 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. The video output signal at pin Vo(vid) is 1.35 V (p-p) for nominal vision IF modulation. Noise clipping is provided. SIF amplifier and SIF 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 signal (average level of FM carrier) and controls the SIF amplifier to provide a constant SIF signal to the single reference QSS mixer. |
Аналогичный номер детали - TDA9808 |
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Аналогичное описание - TDA9808 |
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