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LA1838 (IC1): FM AM IF AMP&detector, FM MPX decoder
1. Block Diagram
30
29
28
REG
AM
ALC
AM
MIX
OSC
BUFF
SD
COMP
FM
AM/FM
S-CLRVE
S-METER
IF-BUFF
PM
FM IF
DET
1
2
3
2. Pin Function
Pin
Symbol
I/O
No.
FM IN
I
This is an input terminal of FM IF
1
signal.
AM MIX
2
O
This is an out put terminal for AM
mixer.
3
I
FM IF
Bypass of FM IF
AM IF
4
I
Input of AM IF Signal.
5
GND
This is the device ground terminal.
6
TUNED
O
When the set is tuning, this terminal
becomes "L".
STEREO
7
O
Stereo indicator output. Stereo "L",
Mono: "H"
8
VCC
This is the power supply terminal.
9
FM DET
FM detect transformer.
10
AM SD
This is a terminal of AM ceramic filter.
O
11
FM VSM
Adjust FM SD sensitivity.
12
AM VSM
O
Adjust AM SD sensitivity.
13
I/O
MUTE
When the signal of IF REQ of IC121(
LC72131) appear, the signal of FM/AM
IF output. //Muting control input.
Change over the FM/AM input.
14
FM/AM
I
"H" :FM, "L" : AM
MONO/ST O
Stereo : "H", Mono: "L"
15
27
26
25
24
FM
RF.AMP
AGC
DET
AM IF
AM
S-METER
TUNING
STEREO
DRIVE
DRIVE
GND
5
4
6
7
Function
23
22
21
20
DECODER
ANIT-BIRDIE
STEREO
P-DET
5N
SW
FF
VCO
38k
384KHz
VCC
8
9
10
11
Pin
I/O
Symbol
No.
16
L OUT
O
Left channel signal output.
17
R OUT
O
Right channel signal output.
18
L IN
Input terminal of the left channel post
I
AMP.
Input terminal of the right channel
19
I
R IN
post AMP.
Mpx Right channel signal output.
20
O
RO
21
LO
O
Mpx Left channel signal output.
22
IF IN
I
Mpx input terminal
23
FM detection output.
FM OUT
O
AM detection output.
24
AM DET
O
This is an AGC voltage input terminal
25
AM AGC
I
for AM
This is an output terminal of voltage
26
AFC
for FM-AFC.
AM RF signal input.
27
AM RF
I
REG
Register value between pin 26 and pin28
28
O
desides the frequency width of the
input signal.
AM OSC
29
This is a terminal of AM Local
oscillation circuit.
30 OSC BUFFER
AM Local oscillation Signal output.
O
UX-F70MD/UX-F72MD
18
19
17
16
MUTE
FF
FF
PILOT
/
19k
19k
LS
DET
2
/
12
13
14
15
Function
1-63
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