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4.8
LA1838 (IC1): FM AM IF amp & Detector, FM MPX decoder
• Block Diagram
30
29
AM
ALC
OSC
BUFF
COMP
FM
S-CLRVE
S-METER
PM
FM IF
DET
1
2
• Pin Function
Pin No.
Symbol
1
FM IN
2
AM MIX
3
FM IF
4
AM IF
5
GND
6
TUNED
7
STEREO
8
VCC
9
FM DET
10
AM SD
11
FM VSM
12
AM VSM
13
MUTE
14
FM/AM
15
MONO/ST
16
L OUT
17
R OUT
18
L IN
19
R IN
20
RO
21
LO
22
MPX IN
23
FM OUT
24
AM DET
25
AM AGC
26
AFC
27
AM RF
28
REG
29
AM OSC
30
OSC BUFFER
1-32 (No.22062)
28
27
26
25
REG
AM
FM
MIX
RF.AMP
AGC
DET
AM IF
SD
AM
S-METER
AM/FM
IF-BUFF
TUNING
DRIVE
GND
5
3
4
6
I/O
I
This is an input terminal of FM IF signal.
O
This is an out put terminal for AM mixer.
I
Bypass of FM IF
I
Input of AM IF Signal.
-
This is the device ground terminal.
O
When the set is tunning, this terminal becomes "L".
O
Stereo indicator output. Stereo "L", Mono: "H"
-
This is the power supply terminal.
-
FM detect transformer.
-
This is a terminal of AM ceramic filter.
O
Adjust FM SD sensitivity.
O
Adjust AM SD sensitivity.
I/O When the signal of IF REQ of IC121(LC72131) appear, the signal of FM/AM IF output. //Muting
control input.
I
Change over the FM/AM input. "H" :FM, "L" : AM
O
Stereo : "H", Mono: "L"
O
Left channel signal output.
O
Right channel signal output.
I
Input terminal of the Left channel post AMP.
I
Input terminal of the Right channel post AMP.
O
Mpx Right channel signal output.
O
Mpx Left channel signal output.
I
Mpx input terminal
O
FM detection output.
O
AM detection output.
I
This is an AGC voltage input terminal for AM
-
This is an output terminal of voltage for FM-AFC.
I
AM RF signal input.
O
Register value between pin 26 and pin28 besides the frequency width of the input signal.
-
This is a terminal of AM Local oscillation circuit.
O
AM Local oscillation Signal output.
24
22
21
23
DECODER
ANIT-BIRDIE
STEREO
P-DET
VCO
384KHz
STEREO
DRIVE
VCC
8
9
7
10
Function
20
19
18
17
MUTE
5N
SW
FF
FF
PILOT
FF
38k
/
19k
19k
LS
DET
2
/
11
12
13
14
16
15
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