TELEFUNKEN Semiconductors

U4460BG

Preliminary Information

Rev. A1: 15.08.1995

3 (9)

FPLL, VCO and AFC

The FPLL circuit (frequency phase locked loop) consists

of a frequency and phase detector to generate control

voltage for the VCO tuning. In the locked mode the VCO

is controlled by the phase detector and in unlocked mode

the frequency detector is superimposed. The VCO

operates with an external resonance circuit (L and C par-

allel) and is controlled by internal varicaps. The VCO

control voltage is also converted to a current and

represents the AFC output signal at Pin 23.

A practicable VCO alignment of the external coil is the

adjustment to zero AFC output current at Pin 23. At centre

frequency the AFC output current is equal to zero. The

optional potentiometer at Pin 27 allows an offset

compensation of the VCO phase for improved sound

quality (fine adjustment). Without a potentiometer (open

circuit at Pin 27) this offset compensation is not active.

The oscillator signal passes a phase shifter and supplies

the in–phase signal (0) and the quadrature signal (90) of

the generated picture carrier.

Video demodulation and amplifier

The video IF signal, which is applied from the gain

controlled IF amplifier, is multiplied with the inphase

component of the VCO signal. The video demodulator is

designed for low distortion and large bandwidth. The

demodulator output signal passes an integrated low pass

filter for attenuation of the residual vision carrier and is

fed to the video amplifier. The video amplifier is realized

by an operational amplifier with internal feedback and 8

MHz bandwidth (–3dB). The video signal is fed to VIF–

AGC and to the video output buffer. This amplifier with

6dB gain offers easy adaption of the sound trap. For

nominal video IF modulation the video output signal at

Pin 13 is 2 V (peak to peak value).

Internal voltage stabilizer

The

internal

bandgap

reference

ensures

constant

performance

independant

of

supply

voltage

and

temperature.

Absolute maximum values

Reference point pin 3 (8, 17), unless otherwise specified

Parameters

Symbol

Value

Unit

Supply voltage

Pin 24

9.0

V

Supply current

Pin 24

85

mA

P

765

mW

Output currents

Pin 13

5

mA

External voltages

Pin 5, 6, 7, 11, 13, 18,

19, 27

+ 4.5

V

Pin 20,21

+ 3.5

V

Pin 12

+ 13.5

V

Pin 20,23

V

Junction temperature

+125

°C

Storage temperature

–25 to +125

°C

Electrostatic handling *)

all pins

t.b.f.

V

*) Equivalent to discharging a 200 pF capacitor through a 0 resistor

Operating range

Parameters

Symbol

Value

Unit

Supply voltage range

Pin25

4.5 to 9.0

V

Ambient temperature

0 to +85

°C