TDA9813T 查看數據表（PDF） - Philips Electronics

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TDA9813T

VIF-PLL with QSS-IF and dual FM-PLL demodulator

Philips Electronics 

Philips Semiconductors

VIF-PLL with QSS-IF and

dual FM-PLL demodulator

Product specification

TDA9813T

FUNCTIONAL DESCRIPTION

The integrated circuit comprises the functional blocks as

shown in Fig.1:

• Vision IF amplifier

• Tuner and VIF-AGC

• Frequency Phase Locked Loop (FPLL) detector

• VCO, Travelling Wave Divider (TWD) and AFC

• Video demodulator and amplifier

• Video buffer

• SIF amplifier and SIF-AGC

• Single reference Quasi Split Sound (QSS) mixer

• FM-PLL demodulator

• Internal voltage stabilizer and 1⁄2VP reference.

Vision IF amplifier

The vision IF amplifier consists of three AC-coupled

differential amplifier stages. Each differential stage

comprises a feedback network controlled by emitter

degeneration.

Tuner and VIF-AGC

The AGC capacitor voltage is transferred to an internal IF

control signal, and is fed to the tuner AGC to generate the

tuner AGC output current (open-collector output).

The tuner AGC takeover point can be adjusted. This

allows the tuner and the SAW filter to be matched to

achieve the optimum IF input level.

The AGC detector charges/discharges the AGC capacitor

to the required voltage for setting of VIF and tuner gain in

order to keep the video signal at a constant level.

Therefore the sync level of the video signal is detected.

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 frequency detector or phase

detector is converted into 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 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 actually double the PC

frequency is generated by the frequency-phase detector

(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 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 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. 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. 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.

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 signals

(average level of FM carriers) and controls the SIF

amplifier to provide a constant SIF signal to the single

reference QSS mixer.

1999 Sep 16

6

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