LA1780 データシートの表示（PDF） - SANYO -> Panasonic

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LA1780

Single-Chip Tuner IC for Car Radios

SANYO -> Panasonic 

Continued from preceding page.

Pin No.

Function

30

Noise canceller input

31

AM/FM detector output

LA1780M

Description

Pin 30 is the noise canceller input.

The input impedance is 50 kΩ.

Pin 31 is the AM and FM detector

output

In FM mode, this is a low-

impedance output.

In AM mode, the output

impedance is 10 kΩ.

To improve the low band

separation, use a coupling

capacitor of over 10 µF.

FM

detector

output

AM

detector

Equivalent circuit

Noise

canceller

FM S-meter output block

MRC AC input block

32

IF S-meter output and MRC

DC input

Adjust the external 1-kΩ resistor

to attenuate the MRC AC input

and control the circuit.

MRC input

33

Mute drive output

•The muting time constant is

determined by an external RC

circuit as described below.

Attack time: TA = 10 kΩ × C1

Release time: TR = 50 kΩ × C1

•Noise convergence adjustment

The noise convergence can be

adjusted when there is no input

signal by inserting a resistor

between pin 33 and ground.

•Muting off function

Ground pin 33 through a 4-kΩ

resistor.

Band

muting

SD circuit

Continued on next page.

No. 5724-13/38

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