Ordering number : ENN6655
LA1787M
Monolithic Linear IC
Single-Chip Tuner IC
for Car Radios
http://onsemi.com
Overview
The LA1787M integrates all six blocks required in a car radio tuner on a single chip.
Functions
• FM front end
• AM up-conversion
• FM IF
• FM/AM switch
• Noise canceller
• MRC
• Multiple
Features
• Improved noise reduction methods
— The FM front end provides excellent 3-signal characteristics equivalent to those of the LA1193M.
— Superlative listenability due to improved medium and weak field noise canceller characteristics.
— Improved separation characteristics
— Anti-birdie filter
— Improved AM and FM thermal characteristics
— Excellent FM signal meter linearity
— Modified N.C. circuit for improved noise rejection
• Improved AM adjacent channel interference characteristics (40 kHz)
• Double conversion AM tuner (up conversion) Reduces the number of external components required as compared to
earlier double conversion tuners, in particular, no crystal is required (when used in conjunction with the LC72144).
• Sample-to-sample variation reduction circuit built into the FM IF circuit.
(Fixed resistors are used for the SD, keyed AGC, mute on adjustment, ATT, SNC, and HCC functions.)
• Improved FM separation temperature characteristics
• The LA1787 inherits the block arrangement of the LA1780M and supports pin-compatible designs.
Package Dimensions
unit : mm (typ)
0.8
1.0
17.2
14.0
0.35
1.6
1.0
0.15
1.6
1.0
33
48
32
0.8
17.2
14.0
49
1
16
15.6
3.0max
1.0
17
64
0.8
Semiconductor Components Industries, LLC, 2011
January, 2011
0.1
2.7
Allowable power dissipation,
Pd max mW
QIP64E(14X14)
Mounted on a 40 x 80 x 1.3 mm
glass epoxy printed circuit board
Independent IC
Ambient temperature, Ta
C
72602RM (OT) No. 6655-1/54
LA1787M
Specifications
Maximum Ratings at Ta = 25°C
Parameter
Symbol
Maximum supply voltage
Allowable power dissipation
Conditions
VCC1 max
Pins 6, 40, and 61
VCC2 max
Pins 7, 45, 54, 59, and 60
Pd max
Ratings
Unit
9
Ta ≤ 55°C
V
12
V
950
mW
Operating temperature
Topr
–40 to +85
°C
Storage temperature
Tstg
–40 to +150
°C
Operating Conditions at Ta = 25°C
Parameter
Symbol
VCC
Recommended supply voltage
VCCST IND
Operating supply voltage range
Conditions
Ratings
Unit
Pins 6, 7, 40, 45, 54, 59, 60, and 61
8
V
Pin 26
5
V
7.5 to 9.0
V
VCC op
Operating Characteristics at Ta = 25°C, VCC= 8.0V, in the specified test cricuit for the FM IF input
Ratings
Parameter
Symbol
Conditions
min
typ
max
unit
[FM Characteristics] At the FM IF input
Current drain
Demodulation output
Pin 31 demodulation output
Channel balance
Total harmonic distortion
ICCO-FM
VO-FM
VO-FM31
CB
No input, I40 + I45 + I54 + I59 + I60 + I61
60
94
110
mA
10.7 MHz, 100dBµ, 1 kHz, 100%mod, The pin 15 output
205
310
415
mVrms
10.7 MHz, 100dBµ, 1 kHz, 100%mod, The pin 31 output
190
295
380
mVrms
The ratio between pins 15 and 16 at 10.7 MHz, 100 dBµ, 1 kHz
–1
0
+1
dB
0.3
1
THD-FM mono
10.7 MHz, 100 dBµ, 1 kHz, 100% mod, pin 15
Signal-to-noise ratio: IF
S/N-FM IF
10.7 MHz, 100 dBµ, 1 kHz, 100% mod, pin 15
75
82
dB
AM suppression ratio: IF
AMR IF
10.7 MHz, 100 dBµ, 1 kHz, fm = 1 kHz, 30% AM, pin 15
55
68
dB
Att-1
10.7 MHz, 100 dBµ, 1 kHz. The pin 15
attenuation when V33 goes from 0 to 2 V
5
10
15
dB
Att-2
10.7 MHz, 100 dBµ, 1 kHz. The pin 15
attenuation when V33 goes from 0 to 2 V*1
15
20
25
dB
Att-3
10.7 MHz, 100 dBµ, 1 kHz. The pin 15
attenuation when V33 goes from 0 to 2 V*2
28
33
38
dB
10.7 MHz, 100 dBµ, L+R = 90%, pilot = 10%. The pin 15 output
ratio
30
40
Muting attenuation
Separation
Separation
Stereo on level
ST-ON
The pilot modulation such that V26 < 0.5 V
1.2
2.4
Stereo off level
ST-OFF
The pilot modulation such that V26 > 3.5 V
0.6
1.6
Main total harmonic distortion
THD-Main L
10.7 MHz, 100 dBµ, L+R = 90%, pilot = 10%. The pin 15 signal
Pilot cancellation
PCAN
10.7 MHz, 100 dBµ, pilot = 10%.
The pin 15 signal/the pilot level leakage. DIN audio
SNC output attenuation
AttSNC
10.7 MHz, 100 dBµ, L-R = 90%, pilot = 10%.
V28 = 3 V → 0.6 V, pin 15
%
dB
4.4
%
%
0.3
1.2
%
20
30
dB
1
5
9
dB
0.5
4.5
8.5
dB
AttHCC-1
10.7 MHz, 100 dBµ, 10 kHz, L+R = 90%, pilot = 10%.
V29 = 3 V → 0.6 V, pin 15
AttHCC-2
10.7 MHz, 100 dBµ, 10 kHz, L+R = 90%,
pilot = 10%. V29 = 3 V → 0.1 V, pin 15
6
10
14
dB
100 dBµ, 10.7 MHz, 30% modulation. The IF input such
that the input reference output goes down by 3 dB
33
40
47
dBµ
The IF input level (unmodulated) when V33 = 2 V
27
35
43
dBµ
The IF input level (unmodulated) (over 100 mV rms)
such that the IF counter buffer output goes on
54
62
70
dBµ
54
62
70
dBµ
VIFBUFF-FM
10.7 MHz, 100 dBµ, unmodulated. The pin 23 output
130
200
270
mVrms
VSM FM-1
No input. The pin 24 DC output, unmodulated
0.0
0.1
0.3
V
VSM FM-2
50 dBµ. The pin 24 DC output, unmodulated
0.4
1.0
1.5
V
VSM FM-3
70 dBµ. The pin 24 DC output, unmodulated
2.0
2.7
3.5
V
VSM FM-4
100 dBµ. The pin 24 DC output, unmodulated
4.7
5.5
6.2
V
Muting bandwidth
BW-mute
100 dBµ. The bandwidth when V33 = 2 V, unmodulated
150
220
290
kHz
Mute drive output
VMUTE-100
100 dBµ, 0 dBµ. The pin 33 DC output, unmodulated
0.00
0.03
0.20
V
HCC output attenuation
Input limiting voltage
Muting sensitivity
SD sensitivity
Vi-lim
Vi-mute
SD-sen1 FM
SD-sen2 FM
IF counter buffer output
Signal meter output
Continued on next page.
No. 6655-2/54
LA1787M
Continued from preceding page.
Ratings
Parameter
Symbol
Conditions
min
typ
max
unit
[FM FE Mixer Input
N-AGC on input
VN-AGC
83 MHz, unmodulated.
The input such that the pin 2 voltage is 2.0 V or below
81
88
95
dBµ
W-AGC on input
VWAGC
83 MHz, unmodulated. The input such that the pin 2
voltage is 2.0 V or below. (When the keyed AGC is set to 4.0 V.)
104
110
116
dBµ
83 MHz, 80 dBµ, unmodulated. The FE CF output
19
30
48
mVrms
No input
85
110
165
mVrms
Conversion gain
Oscillator buffer output
A.V
VOSCBUFFFM
[NC Block] NC input (pin 30)
Gate time
τGATE1
Noise sensitivity
NC effect
SN
SN-NC
f = 1 kHz, for a 1-µs, 100-mV p-o pulse
55
µs
The level of a 1 = kHz, 1-µs pulse input that starts
noise canceller operation. Measured at pin 30.
40
mVp-o
The pulse rejection effect provided by the noise canceller.
For a repeated 1-µs wide pulse, frequency = 10 kHz,
150 mV p-o. The ratio of the FM mode pin 15 output
referenced to the AM mode pin 15 output (effective value)
5
[Multipath Rejection Circuit] MRC input (pin 27)
MRC output
MRC operating level
VMRC
MRC-ON
V24 = 5 V
2.2
2.3
2.4
V
The pin 32 input level at f = 70 kHz such that
pin 24 goes to 5 V and pin 27 goes to 2 V
10
15
20
mVrms
[AM Characteristics] AM ANT input
Practical sensitivity
S/N-30
1 MHz, 30 dBµ, fm = 1 kHz, 30% modulation, pin 15
20
Detector output
VO-AM
1 MHz, 74 dBµ, fm = 1 kHz, 30% modulation, pin 15
130
195
270
mVrms
VO-AM31
1 MHz, 74 dBµ, fm = 1 kHz, 30% modulation, pin 31
110
175
230
mVms
VAGC-FOM
1 MHz, 74 dBµ, referenced to the output, the input amplitude
such that the output falls by 10 dB. Pin 15
51
56
61
dB
47
Pin 31 detector output
AGC F.O.M.
Signal-to-noise ratio
S/N-AM
1 MHz, 74 dBµ, fm = 1 kHz, 30% modulation
Total harmonic distortion
THD-AM
1 MHz, 74 dBµ, fm = 1 kHz, 80% modulation
Signal meter output
Oscillator buffer output
Wide band AGC sensitivity
SD sensitivity
IF buffer output
dB
52
dB
0.3
1
%
V
VSM AM-1
No input
0.0
0.2
0.5
VSM AM-2
1 MHz, 130 dBµ, unmodulated
4.8
6
7.3
No input, the pin 15 output
185
230
VOSCBUFF AM1
V
mVrms
W-AGCsen1
1.4 MHz, the input when V46 = 0.7 V
92
98
104
dBµ
W-AGCsen2
1.4 MHz, the input when V46 = 0.7 V (seek mode)
83
89
95
dBµ
SD-sen1 AM
1 MHz, the ANT input level such that the IF counter output turns on.
24
30
36
dBµ
SD-sen2 AM
1 MHz, the ANT input level such that the SD pin goes to the on state.
24
30
36
1 MHz, 74 dBµ, unmodulated. The pin 23 output
200
290
VIFBUFF-AM
dBµ
mVrms
Note: These measurements must be made using the either the IC-51-0644-824 or KS8277 IC socket (manufactured by Yamaichi Electronics).
* 1. When the resistor between pin 58 and ground is 200 kΩ.
* 2. When the resistor between pin 58 and ground is 30 kΩ.
No. 6655-3/54
LA1787M
Function List
FM Front End (Equivalent to the Sanyo LA1193)
• Double input type double balanced mixer
• Pin diode drive AGC output
• MOSFET second gate drive AGC output
• Keyed AGC adjustment pin
• Differential IF amplifier
• Wide band AGC sensitivity setting pin, and narrow
band AGC sensitivity setting pin
• Local oscillator
FM IF
• IF limiter amplifier
• S-meter output (also used for AM) 6-stage pickup
• Multipath detection pin (shared FM signal meter)
• Quadrature detection
• AF preamplifier
• AGC output
• Band muting
• Weak input muting
• Soft muting adjustment pin
• Muting attenuation adjustment pin
• IF counter buffer output (also used for AM)
• SD (IF counter buffer on level) adjustment pin
• SD output (active high) (also used for AM)
Noise Canceller
• High-pass filter (first order)
• Delay circuit based low-pass filter (fourth order)
• Noise AGC
• Pilot signal compensation circuit
• Noise sensitivity setting pin
• Function for disabling the noise canceller in AM
mode
Multiplex Functions
• Adjustment-free VCO circuit
• Level follower type pilot canceller circuit
• HCC (high cut control)
• Automatic stereo/mono switching
• VCO oscillation stop function (AM mode)
• Forced monaural
• SNC (stereo noise controller)
• Stereo display pin
• Anti-birdie filter
AM
• Double balanced mixer (1st, 2nd)
• IF amplifier
• Detection
• RF AGC (narrow/wide)
• Pin diode drive pin
• IF AGC
• Signal meter output (also used for FM)
• Local oscillator circuits (first and second)
• Local oscillator buffer output
• IF counter buffer output (also used by the FM IF)
• SD (IF counter buffer on level) adjustment pin
• SD output (active high) (also used for AM)
• Wide AGC
• Detection output frequency characteristics
adjustment pin (low cut, high deemphasis)
• AM stereo buffer
MRC (multipath noise rejection circuit)
AM/FM switching output (linked to the FM VCC)
No. 6655-4/54
LA1787M
Operating Characteristics and Symbols Used in the Test Circuit Diagrams
Switches (SW)
Switch on = 1, SW off = 0
There are two switches that use signal transfer.
— SW2: switches between the mixer input and the IF input.
— SW4: switches between noise canceler input and IF output + noise canceler input.
Types of SG used
PG1 (AC1)
Used for noise canceler testing. A pulse generator and an AF oscillator are required.
AC2
Used for FM front end testing. Outputs an 83 MHz signal.
AC3
Used for FM IF, noise canceler, and MPX testing. Outputs a 10.7 MHz signal. Stereo modulation must be possible.
AC4
Used for AM testing. Outputs 1 MHz and 1.4 MHz signals.
AC5
Used with the MRC. Can also be used for AF and OSC.
Power supply
VCC
8V
VCC1
5V
VCC2
0.1 V / 0.7 V / 2 V / 4 V
VCC3
0.1 V / 0.6 V / 2 V
SD, stereo, seek/stop
These levels
must be variable.
Keyed AGC, Mute ATT
HCC, SNC, SASC (MRC)
• Switches
Parameter
ON
SW1
AM/FM switching. The FE VCC is supplied to pin 62.
SW2
FM IF switching. Pin 51/FE output
SW3
For conversion gain testing
SW4
For switching between noise canceler input and IF output + noise canceler.
SW5
High-speed SD
SW6
SEEK/STOP (IF BUFF ON/OFF)
SW7
SW8
SW9
For pilot cancellation testing
SW10
Mute off (pin 33)
OFF
FM
AM
FE IF OUT (A)
AC3 (B)
Conversion gain measurement (A)
Other/purposes
AC1 (A)
Other/purposes
High-speed SD
Other/purposes
STOP
Seek (IF buffer output)
MUTE ATT 200 kΩ
MUTE 200 kΩ
OFF
MUTE ATT 30 kΩ
MUTE 30 kΩ
OFF
When pilot cancellation is used
When pilot cancellation is not used
MUTE OFF
MUTE ON
• Trimmers (variable resistors)
VR1
Separation adjustment
VR2
Pilot cancellation adjustment
Test Points
• DC voltages
VD1
FM RF AGC voltage
Pin 2
VD2
AM/FM SD, AM Tweet, FM stereo indicator
Pin 26
VD3
AM/FM S-meter
Pin 24
VD4
MRC output
Pin 27
VD5
Mute drive output
Pin 33
VD6
AM antenna damping voltage
Pin 46
VD7
N.C. Gate time
Pin 8
• AC voltages
VA1
AM/FM OSC Buff
Pin 4
VA2
First IF output
Pin 53 → CF → pin 51 load level (10.7 MHz)
VA3
IF counter buffer
Pin 23 (10.7 MHz/450 kHz)
VA4
MPX OUT Left ch
Pin 15 (AF)
VA5
MPX OUT Right ch
Pin 16 (AF)
No. 6655-5/54
LA1787M
Pin Descriptions
Pin No.
Function
Description
Equivalent circuit
VCC
62 pin
ANT
RF
AGC
1
Antenna damping drive
1000pF
An antenna damping current flows
when the RF AGC voltage (pin 2)
reaches VCC – VD.
300Ω
100Ω
1
100Ω
1000pF
A13555
VCC
FET
2nd GATE
2
RF AGC
+
Used to control the FET
second gate.
12kΩ
2
ANT
N
AGC
DET
DAMPING
DRIVER
W
AGC
DET
VCC
KEYED
AGC
A13556
3
F.E.GND
VCC
4
4
OSC
Oscillator connection
25pF
2kΩ
VT
20pF
A13557
7
VCC
7
AM OSC
AM first oscillator
This circuit can oscillator up to the
SW band.
An ALC circuit is included.
ALC
A13558
Continued on next page.
No. 6655-6/54
LA1787M
Continued from preceding page.
Pin No.
Function
Description
Equivalent circuit
3kΩ
15kΩ
3kΩ
8
9
Noise AGC sensitivity
AGC adjustment
After setting up the medium field
(about 50 dBµ) sensitivity with the
noise sensitivity setting pin (pin 8),
set the weak field (about 20 to
30 dBµ) sensitivity with the AGC
adjustment pin (pin 9)
200Ω
8
9
3kΩ
+
0.47µF
1MΩ
0.01µF
A13559
0.01µF
13
11
12
Memory circuit connection
6800pF
12
3.9kΩ
11
VCC
Recording circuit used during
noise canceller operation.
Differential
amp
Gate
circuit
LPF
A13560
VCC
30kΩ
13
Pilot input
PLL
Pin 13 is the PLL circuit input pin.
N.C
12
13
0.01µF
A13561
14
N.C, MPX, MRC, GND
Ground for the N.C., MPX, and
MRC circuits.
Continued on next page.
No. 6655-7/54
LA1787M
Continued from preceding page.
Pin No.
Function
Description
Equivalent circuit
VCC
15
16
MPX output (left)
MPX output (right)
Deemphasis
50 µs: 0.015 µF
75 µs: 0.022 µF
3.3kΩ
3.3kΩ
15
16
0.015µF
0.015µF
A13562
VCC
20kΩ
17
Pilot canceller signal output
Adjustment is required since the
pilot signal level varies with the
sample-to-sample variations in
the IF output level and other
parameters.
6.7kΩ
10kΩ
17
18
0.01µF
100kΩ
A13563
VCC
18
Pilot canceller signal output
Pin 18 is the output pin for the
pilot canceller signal.
1.5kΩ
17
18
0.01µF 100kΩ
A13564
Continued on next page.
No. 6655-8/54
LA1787M
Continued from preceding page.
Pin No.
Function
Description
Equivalent circuit
DECODER
Composite
signal
19
Separation
adjustment pin
5kΩ
4kΩ
Use a trimmer to adjust the
subdecoder input level.
(The output level is not modified in
mono and main modes.)
19
30kΩ
0.047µF
A13565
CSB
912
JF108
20
VREF
20
VCO
The oscillator frequency is 912 Hz.
KBR-912F108
(Kyocera Corporation)
CSB-912JF108
(Murata Mfg. Co., Ltd.)
10pF
A13566
VREF
15kΩ
PHASE COMP.
PHASE COMP.
+
15kΩ
19kΩ
21
22
+
+
21
22
A13567
Continued on next page.
No. 6655-9/54
LA1787M
Continued from preceding page.
Pin No.
Function
Description
Equivalent circuit
4.9V
23
IF counter buffer seek/stop
switching
This pin functions both as the IF
counter buffer (AC output) and as
the seek/stop switch pin.
The voltage V23 switches
between the following three
modes.
During FM reception:
5 V: Seek mode
2.5 V: Forced SD mode
0 V: Reception mode
AM reception
(two modes: 0 and 5 V)
5 V: Seek mode
0 V: Reception mode
+
–
50kΩ
+
–
AM MUTE
1.3V
VCC
IF counter
buffer
10kΩ
+
–
SW
150Ω
50F
SD
23
51kΩ
STOP
IF
BUFF.
Forced SEEK
SD: 2.5V 5V
A13568
VCC
FM
S-meter
24
32
AM/FM signal meter
Dedicated FM signal meter
Fixed-current drive signal meter
output
In AM mode, pin 32 outputs a
1-mA current. Thus the HCC
circuit is turned off.
32
10kΩ
AM
S-meter
24
10kΩ
AM/FM
SW
Outputs a 1-mA
current during AM
reception
MRC
AM/FM
SW
A13569
26
Stereo indicator for the SD pin
The voltage V23 switches
between three modes as follows.
FM reception:
5 V: The SD pin operates linked
to the IF counter buffer.
2.5 V: Forced SD mode: operates
as the SD pin.
0.7 V: Reception mode: stereo
indicator
AM reception: (two modes: 0 and 5 V)
5 V: Operates as the seek SD pin.
0 V: Reception mode. Not used.
AM/FM
SD
Stereo
indicator
Seek/stop
switching
26
100kΩ
VDD
A13570
Continued on next page.
No. 6655-10/54
LA1787M
Continued from preceding page.
Pin No.
Function
Description
Equivalent circuit
VCC
VCC
C2
+
2µA
27
27
MRC control voltage time
constant
The MRC detector time constant
is determined by a 100 Ω resistor
and C2 when discharging and by
the 2-µA current and C2 when
charging.
100Ω
Pin 28
A13571
VREF
28
SNC control input
The sub-output is controlled by a
0 to 1-V input.
28
A13572
VREF
The high band frequency output is
controlled by a 0 to 1-V input.
29
HCC control input
It can also be controlled by the
MRC output.
Use a resistor of at least 100 kΩ
when controlling with the pin 32
FM S-meter signal.
32
29
+
1µF
A13573
Continued on next page.
No. 6655-11/54
LA1787M
Continued from preceding page.
Pin No.
Function
Description
Equivalent circuit
VCC
FM
detector
output
31
30
31
Noise canceller input
Pin 30 is the noise canceller input.
The input impedance is 50 kΩ.
AM/FM detector output
Pin 31 is the AM and FM detector
output
In FM mode, this is a lowimpedance output.
In AM mode, the output
impedance is 10 kΩ.
To improve the low band
separation, use a coupling
capacitor of over 10 µF.
10kΩ
VCC
1µF
AM
detector
+
30
Noise
canceller
50kΩ
4.2V
A13574
VCC
32
32
IF S-meter output and MRC
DC input
FM S-meter output block
MRC AC input block
Adjust the external 1-kΩ resistor
to attenuate the MRC AC input
and control the circuit.
10kΩ
+
1µF
1kΩ
MRC input
A13575
C1
+
0.1µF
•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
33
Mute drive output
•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.
33
VCC
50kΩ
MUTE
AMP.
SEEK
OFF
SOFT
MUTE
10kΩ
HOLE
DET
Band
muting
50kΩ
SD circuit
A13576
Continued on next page.
No. 6655-12/54
LA1787M
Continued from preceding page.
Pin No.
Function
Description
Equivalent circuit
0.1µF
R1
VREF
VCC
C
37
•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.
35
34
Quadrature
detector
HOLE
DET
390Ω
AGC
QD output
QD input
VREF
36
VCC
•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.
34
35
36
37
R2
3pF
V37 = 4.9 V
1kΩ
IF limitter amplifier
Band
muting
A13577
R
SD ADJ
38
38
FM SD ADJ
A 130-µA current flows from pin
38 and, in conjunction with the
external resistance R, determines
the comparison voltage.
130µA
+
–
SD
Comparator
24
S-meter
A13578
S-meter
24
6.4kΩ
3.6kΩ
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
KEYED
AGC
+
–
39
1.3V
90µA
VCC
AM IF out
50pF
150Ω
A13579
Continued on next page.
No. 6655-13/54
LA1787M
Continued from preceding page.
Pin No.
Function
Description
Equivalent circuit
VCC
20kΩ
+
41
HCC capacitor
20kΩ
The HCC frequency characteristics
are determined by the external
capacitor connected at this pin.
41
2200pF
A13580
This pin is used to change the
frequency characteristics of the
unneeded audio band under
100 Hz in AM mode to produce
a clear audio signal.
VCC
C
42
42
AM L.C. pin
Note: The LC capacitor must be
connected between this pin
and VCC (pin 40).
This is because the detector
circuit operates referenced
to VCC.
VCC
DET
50kΩ
1kΩ
+
–
50kΩ
The cutoff frequency fC is
determined by the following
formula.
1kΩ
A13581
fC = 1/2π × 50 kΩ × C
VCC
19kHz∠0°
BIAS
30kΩ
43
Pilot detector
Inserting a 1-MΩ resistor between
pin 43 and VCC will force the IC
to mono mode.
30kΩ
+
30kΩ
43
1µF
+
A13582
Continued on next page.
No. 6655-14/54
LA1787M
Continued from preceding page.
Pin No.
Function
Description
Equivalent circuit
+
0.022µF
240kΩ
42
44
IF AGC
G1; Used for time constant
switching during seeks.
• Reception
τ = 2.2 µF × 300 kΩ
• Seek
τ = 2.2 µF × 10 Ω
The external capacitors are
connected to VCC.
This is because the IF amplifier
operates referenced to VCC.
VCC
C
2.2µF
44
VCC
DET
50kΩ
50kΩ
IF
AGC
G1
SEEK
ON
10Ω
A13583
Pin 40 VCC
45
Pin 40 VCC
45
IF output
The IF amplifier load
DET
A13584
VCC
50pF
46
100Ω
46
AM antenna damping
drive output
Wide band AGC input
I46 = 6 mA (maximum)
This is the antenna damping
current.
20kΩ
VCC
W.AGC AMP.
ANT DAMPING
DRIVER
A13585
Continued on next page.
No. 6655-15/54
LA1787M
Continued from preceding page.
Pin No.
Function
Description
Equivalent circuit
30kΩ
R
47
VCC
FM muting on level
adjustment
140µA
+
–
47
Modify the value of the external
resistor to adjust the muting on
level.
Pin 24
Inverter
MUTE
A13586
VCC
5.6V
48
57
RF AGC bypass
RF AGC
RF AGC rectification capacitor
The low frequency distortion is
determined as follows:
Increasing C48 and C57 improves
the distortion but makes the
response slower.
Reducing C48 and C57
aggravates the distortion but
makes the response faster.
10kΩ
48
+
–
+
Antenna
damping
3.3µF
For AGC use
57
+
47µF
A13587
2.6V
50
51
IF bypass
FM IF input
Due to the high gain of the limiter
amplifer, care must be taken when
choosing the grounding point for
the limiter amplifer input capacitor
to prevent oscillation.
10kΩ
10kΩ
50
0.022µF
330Ω
51
IF in
A13588
2kΩ
100Ω
52
IF input
The input impedance is 2 kΩ.
52
A13589
Continued on next page.
No. 6655-16/54
LA1787M
Continued from preceding page.
Pin No.
Function
Description
Equivalent circuit
VCC
IF OUT 53
• Input and output pin or the first
IF amplifier
• Inverting amplifier
53
56
IF amplifier output
IF amplifier input
300Ω
300Ω
V56 = 2 V
Input impedance: RIN = 330 Ω
2.75V
V53 = 5.3 V
Output impedance
ROUT = 330 Ω
IF IN 56
A13590
Pin 40 VCC
Pin 40 VCC
54
54
49
Mixer output: 130 µA
Mixer input
OSC
The mixer coil connected to the
pin 54 mixer output must be
wired to VCC (pin 40).
The pin 49 mixer input
impedance is 330 Ω
49
330Ω
A13591
62 pin
VCC
W-AGC
N-AGC
Pins 55 and 58 include built-in
DC cut capacitors.
The AGC on level is determined
by the values of the capacitors
C1 and C2.
55
58
W-AGC IN
AM SD ADJ
N-AGC IN
Muting attenuation
adjustment pin
Pin 55 functions as the SD
sensitivity adjustment pin in
AM mode.
The output current I55 is 50 µA,
and V55 varies depending on the
value of the external resistor.
The SD function operates by
comparing V55 with the S-meter
voltage.
55
30pF
C1
MIX
IN
50pF
58
C2
50µA
MIX
OUT
+
–
AM SD
Signal meter
A13592
Continued on next page.
No. 6655-17/54
LA1787M
Continued from preceding page.
Pin No.
Function
Description
Equivalent circuit
1ST.IF
OSC
59
Double balanced mixer
Pins 59 and 60 are the mixer
10.7-MHz output
VCC
60
59
60
Mixer output
63
64
Mixer input
Pins 63 and 64 are the mixer
input.
This is an emitter insertion type
circuit, and the amount of
insertion is determined by the
capacitors C1 and C2.
Note:The lines for pins 63 and 64
must be kept separated from
the lines for pins 59 and 60.
30Ω
VCC
C1
63
RF AMP
5pF
C2
64
5pF
620Ω
620Ω
A13593
Pin 6 functions both as the FM
front end VCC and the AM/FM
switching circuit.
6
Front end VCC AM/FM
switching
V6 voltage
VCC
SD
+
–
+
FM.F.E
AGC 100kΩ
Mode
When 8 V → FM
510Ω
6
8V
OPEN → AM
AM/FM
switching circuit
3.3V
3
GND
A13594
AM 1st
MIX
to RF
Amp.
62
62
1st MIX
INPUT
First mixer input
The input impedance is about
10 kΩ.
10kΩ
2.1V
A13595
10kΩ
5.6V
10
AM 2nd OSC
Crystal oscillator circuit
The Kinseki, Ltd. HC-49/U-S and
a CL of 20 pF must be used.
20pF
to 2nd
MIX
33pF
10
X tal
A13596
No. 6655-18/54
+
10kΩ
VREF
AM LC
PILOT DET
1µF
0.022µF
2200pF
100µF
0.22µF
11kΩ
IF7
2.2µF
3.3µF
QD IN
QD OUT
AFC IN
0.47µF
FM SD ADJ. 30kΩ
KEYED AGC 6.8kΩ
0.47µF
MUTE DRIVE
CHCC
48
47
46
45
44
43
42
41
40
39
38
37
36
35
34
33
1µF
32
1µF
15pF
15pF
50
0.022µF
49
31
NC-IN
30
100kΩ
47µF
51
29
GND
52
28
53
27
26
100kΩ
54
55
2.7kΩ
56
25
5V
24
AM/FM
S-METER 0.47µF
330Ω
57
23
22
59
58
21
60
61
20
0.022µF
19
+
–
62
18
17
100kΩ
18pF
63
SEP.ADJ
0.022µF
100F 100kΩ
30kΩ
AM
OSC
N.C.MPX
GND
0.015µF
0.015µF
FM/AM VSM
1000pF
ANT D
RF AGC
FE GND
18pF
OSC
10kΩ
1000pF
100kΩ
39pF
9pF
100kΩ
LEFT CH.
300pF
10µF
10µF
AM VCC
AM ANT IN
AM RF GND
FM ANT IN
FM/AM VT
FM GND
2kΩ
AM/FM OSC BUFF
25pF
20pF
0.022µF
0.022µF
10.26MHz
1µF
10µF
10µF
RIGHT CH.
NC MPX GND
0.022µF
1MΩ
0.01µF
0.47µF
3SK263 180Ω
100kΩ
64
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
FMIF AM GND
FMIF AM NC MPX VCC
MPX
OUT
200kΩ
68pF
2.2kΩ
240kΩ
240kΩ
100kΩ
100kΩ
10kΩ
1kΩ
4.7kΩ
51kΩ
22kΩ
22kΩ
22kΩ
10kΩ
0.01µF
3SK583
100pF
100pF
100pF
100pF
51kΩ
1.5kΩ
+B
12V
10µF
GND
22kΩ
22kΩ
100kΩ
10kΩ
100µF
7
6
14
15 AM IN
20
19 VSS
7.2MHz
CE
CI
CL
17 VDD
18 PD
DO
16 FM IN
1
2
3
4
5
8
LC7216M
9
13
FM/AM 10
10kΩ
1kΩ
22kΩ
100kΩ
12
11
100µF
5.6V
SEEK→AM/FM SD
STOP→FM ST IND.
9.1V
0.022µF
VCC
+
+
+
+
TO AM STEREO
(IF OUT)
+
+
10kΩ
0.1µF
240kΩ
RFAGC
1µF
HCC
1kΩ
1MH
1kΩ
0.022µF
30Ω
0.22µF
+
50kΩ AM LEVEL
ADJ
DET OUT
100µH
+
0.022µF
100kΩ
FM
100µH
+
MUTE
AMP
Q.DET
METER
ANT
D
OSC
OSC
BUFF
15pF
FM IF IN
FC18
220Ω
30MH
SNC
DC-C AFC
DET CLAMP
L.C.
8200pF AM HC
IF limiter
amplifier
+
BUFF
100Ω
MUTE
DRIVE
HOLE
DET
FMVSM
FM SD
AMVSM
AM SD
IF
AGC
AM IF IN
MRC
+
DET
510kΩ
+
AM SD ADJ
AM MIX OUT
FM WB AGCIN
1µF
IF BUFF
FM IF OUT
10kΩ
SNC
MIX
HCC
IF AM/FM
REG
SW
TWEET
RF AGC
WB AGC
20kΩ
VCO
GND
FE IF IN
FF
19k
