LA1781M 查看數據表（PDF） - SANYO -> Panasonic

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LA1781M

For Car Radios Single-Chip Tuner IC

SANYO -> Panasonic 

Continued from preceding page.

Pin No.

Pin function

24

AM/FM signal meter

32

Dedicated FM signal meter

LA1781M

Pin description

Fixed-current drive signal meter

output.

In AM mode, pin 32 outputs a

1mA current. Thus the HCC

circuit is turned off.

26

Stereo indicator for the SD pin The voltage V23 switches between

three modes as follows.

FM reception :

5V : The SD pin operates linked

to the IF counter buffer.

2.5V : Forced SD mode: operates

as the SD pin.

0.7V : Reception mode: stereo

indicator

AM reception : (two modes : 0 and 5V)

5V : Operates as the seek SD pin.

0V : Reception mode. Not used.

27

MRC control voltage time

constant

The MRC detector time constant is

determined by a 100Ω resistor and C2

when discharging and by the 2μA

current and C2 when charging.

Equivalent circuit

VCC

FM

S-meter

AM

S-meter

AM/FM

SW

32

10kΩ

24

10kΩ

Outputs a 1-mA

current during AM

reception

MRC

AM/FM

SW

AM/FM Stereo

SD

indicator

Seek/stop

switching

26

100kΩ

VDD

VCC

2μA

VCC

C2

27

100Ω

Pin 28

28

SNC control input

The sub-output is controlled by a 0 to

1V input.

VREF

28

Continued on next page.

No.6038-10/48

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