LA1780 Ver la hoja de datos (PDF) - SANYO -> Panasonic

Número de pieza

componentes Descripción

fabricante

LA1780

Single-Chip Tuner IC for Car Radios

SANYO -> Panasonic 

Continued from preceding page.

Pin No.

Function

LA1780M

Description

Equivalent circuit

34

AGC

35

QD output

36

QD input

37

VREF

•The resistor R1 determines the

width of the band muting function.

Increasing the value of R1

narrows the band.

Reducing the value of R1 widens

the band.

•Null voltage

When tuned, the voltage between

pins 34 and 37, V34 – 37, will be 0 V.

The band muting function turns

on when |V34 – 37| ≥ 0.7 V.

V37 = 4.9 V

Quadrature

detector

IF limiter amplifier

Band

muting

38

FM SD ADJ

A 130-µA current flows from pin

38 and, in conjunction with the

external resistance R, determines

the comparison voltage.

39

Keyed AGC

AM stereo buffer

The keyed AGC operates when

the voltage created by dividing the

pin 24 S-meter output voltage by

the 6.4 and 3.6 kΩ resistors

becomes lower than the voltage

determined by the resistor

between pin 39 and ground.

This pin also is used as the AM

stereo IF buffer pin.

Comparator

S-meter

S-meter

Comparator

Continued on next page.

No. 5724-14/38

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