No. 5764-8/11

LA7566

Continued from preceding page.

Pin No.

Symbol

Pin function

Equivalent circuit

11

12

VCO

• VCO tank circuit used for video detection.

See the separately provided documentation for the tank circuit

coil (inductor) specifications.

13

14

VIDEO OUT

EQ FILTER

• Equalizer circuit. This circuit corrects the video signal frequency

characteristics.

• Notes on equalizer amplifier design:

The equalizer amplifier is designed as a voltage follower

amplifier with a gain of about 2.3 dB. When the frequency

characteristics are corrected, connect an inductor, a capacitor,

and a resistor in series between pin 14 and ground.

The equalizer amplifier gain is given by:

R1

AV = —— + 1

Z

Here, R1 is an IC internal resistor with a value of 1 k

Ω. Select Z

according to the desired characteristics. However, care is

required to prevent distortion at the resonant point determined

by Z, where the gain is maximum.

15

16

PAL VIDEO IN

NT VIDEO IN

• Equalizer amplifier inputs.

Pin 15 is for PAL, and pin 16 for NTSC format signals. These

inputs are linked to and switched by the SIF switches.

17

APC FILTER

• PLL detector APC filter connection.

The APC time constants are switched internally in the IC. When

locked, the VCO is controlled over the path A, and the loop gain

is reduced. When unlocked and during weak field reception, the

VCO is controlled over the path B, thus increasing the loop

gain.

We recommend values of:

R = 150 to 390

Ω, and

C = 0.47 µF

for the loop filter constants.

Continued on next page.