72602RM (OT) No. 6655-1/54
http://onsemi.com
Semiconductor Components Industries, LLC, 2011 January, 2011
LA1787M
Overview The LA1787M integrates all six blocks required in a car radio tuner on a single chip.
Functions • FM front end • FM IF • Noise canceller • Multiple • AM up-conversion • FM/AM switch • MRC
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) QIP64E(14X14)
Ordering number : ENN6655
Monolithic Linear IC
Single-Chip Tuner IC for Car Radios
14.017.2
1.0 1.0 1.6
0.150.35
0.1
15.6 0.8
0.8
3.0m
ax
1 16
17
32
3348
49
64
2.7
14.0
17.2
1.0
1.0
1.6
0.8
Mounted on a 40 x 80 x 1.3 mmglass epoxy printed circuit board
Independent IC
All
ow
able
pow
er d
issi
pat
ion,
Pd m
ax m
W
Ambient temperature, Ta C
RatingsParameter Symbol Conditions
min typ maxunit
[FM Characteristics] At the FM IF input
Current drain ICCO-FM No input, I40 + I45 + I54 + I59 + I60 + I61 60 94 110 mA
Demodulation output VO-FM 10.7 MHz, 100dBµ, 1 kHz, 100%mod, The pin 15 output 205 310 415 mVrms
Pin 31 demodulation output VO-FM31 10.7 MHz, 100dBµ, 1 kHz, 100%mod, The pin 31 output 190 295 380 mVrms
Channel balance CB The ratio between pins 15 and 16 at 10.7 MHz, 100 dBµ, 1 kHz –1 0 +1 dB
Total harmonic distortion THD-FM mono 10.7 MHz, 100 dBµ, 1 kHz, 100% mod, pin 15 0.3 1 %
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-110.7 MHz, 100 dBµ, 1 kHz. The pin 15
5 10 15 dBattenuation when V33 goes from 0 to 2 V
Muting attenuation Att-210.7 MHz, 100 dBµ, 1 kHz. The pin 15
15 20 25 dBattenuation when V33 goes from 0 to 2 V*1
Att-310.7 MHz, 100 dBµ, 1 kHz. The pin 15
28 33 38 dBattenuation when V33 goes from 0 to 2 V*2
Separation Separation10.7 MHz, 100 dBµ, L+R = 90%, pilot = 10%. The pin 15 output
30 40 dBratio
Stereo on level ST-ON The pilot modulation such that V26 < 0.5 V 1.2 2.4 4.4 %
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 0.3 1.2 %
Pilot cancellation PCAN 10.7 MHz, 100 dBµ, pilot = 10%. 20 30 dB
The pin 15 signal/the pilot level leakage. DIN audio
SNC output attenuation AttSNC10.7 MHz, 100 dBµ, L-R = 90%, pilot = 10%.
1 5 9 dBV28 = 3 V → 0.6 V, pin 15
AttHCC-1 10.7 MHz, 100 dBµ, 10 kHz, L+R = 90%, pilot = 10%.0.5 4.5 8.5 dB
HCC output attenuationV29 = 3 V → 0.6 V, pin 15
AttHCC-2 10.7 MHz, 100 dBµ, 10 kHz, L+R = 90%, 6 10 14 dB
pilot = 10%. V29 = 3 V → 0.1 V, pin 15
Input limiting voltage Vi-lim 100 dBµ, 10.7 MHz, 30% modulation. The IF input such33 40 47 dBµ
that the input reference output goes down by 3 dB
Muting sensitivity Vi-mute The IF input level (unmodulated) when V33 = 2 V 27 35 43 dBµ
SD-sen1 FM The IF input level (unmodulated) (over 100 mV rms) 54 62 70 dBµ
SD sensitivity such that the IF counter buffer output goes on
SD-sen2 FM 54 62 70 dBµ
IF counter buffer output 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
Signal meter outputVSM 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
Operating Characteristics at Ta = 25°C, VCC= 8.0V, in the specified test cricuit for the FM IF input
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No. 6655-2/54
LA1787M
SpecificationsMaximum Ratings at Ta = 25°C
Operating Conditions at Ta = 25°C
Parameter Symbol Conditions Ratings Unit
Maximum supply voltageVCC1 max Pins 6, 40, and 61 9 V
VCC2 max Pins 7, 45, 54, 59, and 60 12 V
Allowable power dissipation Pd max Ta ≤ 55°C 950 mW
Operating temperature Topr –40 to +85 °C
Storage temperature Tstg –40 to +150 °C
Parameter Symbol Conditions Ratings Unit
Recommended supply voltageVCC Pins 6, 7, 40, 45, 54, 59, 60, and 61 8 V
VCCST IND Pin 26 5 V
Operating supply voltage range VCC op 7.5 to 9.0 V
RatingsParameter Symbol Conditions
min typ maxunit
[FM FE Mixer Input
N-AGC on input VN-AGC83 MHz, unmodulated.
81 88 95 dBµThe input such that the pin 2 voltage is 2.0 V or below
W-AGC on input VWAGC83 MHz, unmodulated. The input such that the pin 2
104 110 116 dBµvoltage is 2.0 V or below. (When the keyed AGC is set to 4.0 V.)
Conversion gain A.V 83 MHz, 80 dBµ, unmodulated. The FE CF output 19 30 48 mVrms
Oscillator buffer output VOSCBUFFFM No input 85 110 165 mVrms
[NC Block] NC input (pin 30)
Gate time τGATE1 f = 1 kHz, for a 1-µs, 100-mV p-o pulse 55 µs
Noise sensitivity SNThe level of a 1 = kHz, 1-µs pulse input that starts
40 mVp-onoise canceller operation. Measured at pin 30.
The pulse rejection effect provided by the noise canceller.
NC effect SN-NCFor a repeated 1-µs wide pulse, frequency = 10 kHz,
5150 mV p-o. The ratio of the FM mode pin 15 output referenced to the AM mode pin 15 output (effective value)
[Multipath Rejection Circuit] MRC input (pin 27)
MRC output VMRC V24 = 5 V 2.2 2.3 2.4 V
MRC operating level MRC-ONThe pin 32 input level at f = 70 kHz such that
10 15 20 mVrmspin 24 goes to 5 V and pin 27 goes to 2 V
[AM Characteristics] AM ANT input
Practical sensitivity S/N-30 1 MHz, 30 dBµ, fm = 1 kHz, 30% modulation, pin 15 20 dB
Detector output VO-AM 1 MHz, 74 dBµ, fm = 1 kHz, 30% modulation, pin 15 130 195 270 mVrms
Pin 31 detector output VO-AM31 1 MHz, 74 dBµ, fm = 1 kHz, 30% modulation, pin 31 110 175 230 mVms
AGC F.O.M. VAGC-FOM1 MHz, 74 dBµ, referenced to the output, the input amplitude
51 56 61 dBsuch that the output falls by 10 dB. Pin 15
Signal-to-noise ratio S/N-AM 1 MHz, 74 dBµ, fm = 1 kHz, 30% modulation 47 52 dB
Total harmonic distortion THD-AM 1 MHz, 74 dBµ, fm = 1 kHz, 80% modulation 0.3 1 %
Signal meter outputVSM AM-1 No input 0.0 0.2 0.5 V
VSM AM-2 1 MHz, 130 dBµ, unmodulated 4.8 6 7.3 V
Oscillator buffer output VOSCBUFF AM1 No input, the pin 15 output 185 230 mVrms
Wide band AGC sensitivityW-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 sensitivitySD-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 dBµ
IF buffer output VIFBUFF-AM 1 MHz, 74 dBµ, unmodulated. The pin 23 output 200 290 mVrms
No. 6655-3/54
LA1787M
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.
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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 DiagramsSwitches (SW)Switch on = 1, SW off = 0There 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.
No. 6655-5/54
LA1787M
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 8 V
VCC1 5 V SD, stereo, seek/stop
VCC2 0.1 V / 0.7 V / 2 V / 4 V These levels Keyed AGC, Mute ATT
VCC3 0.1 V / 0.6 V / 2 V must be variable. HCC, SNC, SASC (MRC)
• Trimmers (variable resistors)
VR1 Separation adjustment
VR2 Pilot cancellation adjustment
• 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)
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
• Switches
Parameter ON OFF
SW1 AM/FM switching. The FE VCC is supplied to pin 62. FM AM
SW2 FM IF switching. Pin 51/FE output FE IF OUT (A) AC3 (B)
SW3 For conversion gain testing Conversion gain measurement (A) Other/purposes
SW4 For switching between noise canceler input and IF output + noise canceler. AC1 (A) Other/purposes
SW5 High-speed SD High-speed SD Other/purposes
SW6 SEEK/STOP (IF BUFF ON/OFF) STOP Seek (IF buffer output)
SW7 MUTE ATT 200 kΩ MUTE 200 kΩ OFF
SW8 MUTE ATT 30 kΩ MUTE 30 kΩ OFF
SW9 For pilot cancellation testing When pilot cancellation is used When pilot cancellation is not used
SW10 Mute off (pin 33) MUTE OFF MUTE ON
Pin No. Function Description Equivalent circuit
3 F.E.GND
7VCC
A L C
A13558
Pin Descriptions
No. 6655-6/54
LA1787M
1
ANT
1000pF
1000pF
100Ω
100Ω
300Ω
VCC 62 pin
RFAGC
A13555
+2
NAGCDET
WAGCDET
KEYEDAGC
ANTDAMPINGDRIVER
VCC
VCC
12kΩFET2nd GATE
A13556
4
VCC
25pF
20pF2kΩVT
A13557
An antenna damping current flows1 Antenna damping drive when the RF AGC voltage (pin 2)
reaches VCC – VD.
2 RF AGCUsed to control the FET second gate.
4 OSC Oscillator connection
AM first oscillator
7 AM OSCThis circuit can oscillator up to theSW band.An ALC circuit is included.
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No. 6655-7/54
LA1787M
Pin No. Function Description Equivalent circuit
13 Pilot input Pin 13 is the PLL circuit input pin.
14 N.C, MPX, MRC, GNDGround for the N.C., MPX, andMRC circuits.
+
8 9
3kΩ
15kΩ3kΩ
3kΩ
1MΩ0.01µF
0.47µF
200Ω
A13559
13 12 11VCC
3.9kΩ0.01µF 6800pF
LPF
Differentialamp Gate
circuit
A13560
12 13
30kΩ
VCC
PLL
N.C
0.01µFA13561
After setting up the medium field (about 50 dBµ) sensitivity with the
8 Noise AGC sensitivity noise sensitivity setting pin (pin 8), 9 AGC adjustment set the weak field (about 20 to
30 dBµ) sensitivity with the AGC adjustment pin (pin 9)
11Memory circuit connection
Recording circuit used during 12 noise canceller operation.
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No. 6655-8/54
LA1787M
Pin No. Function Description Equivalent circuit
15
3.3kΩ3.3kΩ
VCC
0.015µF 0.015µF
16
A13562
17 18
VCC
20kΩ
10kΩ
0.01µF 100kΩ
6.7kΩ
A13563
17 18
VCC
0.01µF
1.5kΩ
100kΩ
A13564
15 MPX output (left)Deemphasis
16 MPX output (right)50 µs: 0.015 µF75 µs: 0.022 µF
Adjustment is required since thepilot signal level varies with the
17 Pilot canceller signal output sample-to-sample variations inthe IF output level and otherparameters.
18 Pilot canceller signal outputPin 18 is the output pin for the pilot canceller signal.
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No. 6655-9/54
LA1787M
Pin No. Function Description Equivalent circuit
20 VCO The oscillator frequency is 912 Hz.KBR-912F108 (Kyocera Corporation)CSB-912JF108 (Murata Mfg. Co., Ltd.)
19
5kΩDECODER
Compositesignal
30kΩ
4kΩ
0.047µF
A13565
20
CSB912JF108
VREF
10pF
A13566
+
+
+
21 22
15kΩ
15kΩ
19kΩ
VREF
A13567
Use a trimmer to adjust the
19Separation subdecoder input level.adjustment pin (The output level is not modified in
mono and main modes.)
21 PHASE COMP.22 PHASE COMP.
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No. 6655-10/54
LA1787M
Pin No. Function Description Equivalent circuit
23
+–
+–
+–
4.9V50kΩ
150Ω
50F
1.3V
10kΩ
51kΩ
STOP
IFBUFF.
ForcedSD: 2.5V
SEEK5V
SD
SW
VCC
AM MUTE
IF counterbuffer
A13568
32
24
10kΩ
10kΩ
VCC
AM/FMSW
FMS-meter
AMS-meter
Outputs a 1-mAcurrent during AMreception
AM/FMSW
MRC
A13569
26
100kΩ
VDD
AM/FMSD
Stereoindicator
Seek/stopswitching
A13570
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This pin functions both as the IF counter buffer (AC output) and asthe seek/stop switch pin.The voltage V23 switchesbetween the following threemodes.
23IF counter buffer seek/stop During FM reception:switching 5 V: Seek mode
2.5 V: Forced SD mode0 V: Reception mode
AM reception(two modes: 0 and 5 V)
5 V: Seek mode0 V: Reception mode
24 AM/FM signal meter Fixed-current drive signal meter output
In AM mode, pin 32 outputs a32 Dedicated FM signal meter 1-mA current. Thus the HCC
circuit is turned off.
The voltage V23 switches between three modes as follows. FM reception:5 V: The SD pin operates linked
to the IF counter buffer.
26 Stereo indicator for the SD pin2.5 V: Forced SD mode: operates
as the SD pin.0.7 V: Reception mode: stereo
indicatorAM reception: (two modes: 0 and 5 V)5 V: Operates as the seek SD pin.0 V: Reception mode. Not used.
No. 6655-11/54
LA1787M
Pin No. Function Description Equivalent circuit
+
27
2µA
100Ω
C2
VCC
VCC
Pin 28
A13571
28
VREF
A13572
+
32
1µF
29
VREF
A13573
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The MRC detector time constant
27 MRC control voltage timeis determined by a 100 Ω resistor
constantand C2 when discharging and bythe 2-µA current and C2 whencharging.
28 SNC control inputThe sub-output is controlled by a0 to 1-V input.
The high band frequency output is controlled by a 0 to 1-V input.
It can also be controlled by the 29 HCC control input MRC output.
Use a resistor of at least 100 kΩwhen controlling with the pin 32FM S-meter signal.
No. 6655-12/54
LA1787M
Pin No. Function Description Equivalent circuit
31
30
+
VCC
VCC
10kΩ
FMdetectoroutput
AMdetector
Noisecanceller
1µF
50kΩ
4.2V
A13574
+
32
VCC
10kΩ
1kΩ
1µF
A13575
MRC input
+
33
HOLEDET
SOFTMUTE
Bandmuting
SEEKOFF
VCC
0.1µF
C1
50kΩ
10kΩ
50kΩ
MUTEAMP.
SD circuit
A13576
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30 Noise canceller inputPin 30 is the noise canceller input. The input impedance is 50 kΩ.
Pin 31 is the AM and FM detectoroutputIn FM mode, this is a low-impedance output.
31 AM/FM detector output In AM mode, the output impedance is 10 kΩ.To improve the low band separation, use a couplingcapacitor of over 10 µF.
FM S-meter output block
32 IF S-meter output and MRCMRC AC input block
DC inputAdjust the external 1-kΩ resistor to attenuate the MRC AC input and control the circuit.
•The muting time constant is determined by an external RCcircuit as described below.Attack time: TA = 10 kΩ × C1Release time: TR = 50 kΩ × C1
•Noise convergence adjustment33 Mute drive output The noise convergence can be
adjusted when there is no inputsignal by inserting a resistorbetween pin 33 and ground.
•Muting off functionGround pin 33 through a 4-kΩresistor.
No. 6655-13/54
LA1787M
Pin No. Function Description Equivalent circuit
37 36 35 34
HOLEDET
Quadraturedetector
Bandmuting
IF limitter amplifier
A13577
0.1µF VREF R1
R2
VCC
VCC
C
390Ω
1kΩ
3pF
24
38
+– SD
Comparator
S-meter
R SD ADJ
130µA
A13578
24
39+–
KEYEDAGC
Comparator
S-meter
A13579
6.4kΩ
3.6kΩ
1.3V
50pF 150Ω
90µA
VCC
AM IF out
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•The resistor R1 determines the width of the band muting function.Increasing the value of R1narrows the band.Reducing the value of R1 widensthe band.
34 AGC35 QD output •Null voltage36 QD input When tuned, the voltage between37 VREF pins 34 and 37, V34 – 37, will be 0 V.
The band muting function turnson when |V34 – 37| ≥ 0.7 V.
V37 = 4.9 V
A 130-µA current flows from pin
38 FM SD ADJ38 and, in conjunction with the external resistance R, determines the comparison voltage.
The keyed AGC operates when the voltage created by dividing thepin 24 S-meter output voltage bythe 6.4 and 3.6 kΩ resistors
39 Keyed AGC becomes lower than the voltageAM stereo buffer determined by the resistor
between pin 39 and ground.
This pin also is used as the AMstereo IF buffer pin.
No. 6655-14/54
LA1787M
Pin No. Function Description Equivalent circuit
41
A13580
+
2200pF
20kΩ
20kΩ
VCC
42
+–
DET
VCC
VCC
C
50kΩ
50kΩ
1kΩ
1kΩ
A13581
+
43
+
VCC
30kΩ
30kΩ
30kΩ
19kHz∠0°BIAS
1µF
A13582
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The HCC frequency characteristics41 HCC capacitor are determined by the external
capacitor connected at this pin.
This pin is used to change thefrequency characteristics of the unneeded audio band under 100 Hz in AM mode to produce a clear audio signal.
Note: The LC capacitor must be connected between this pinand VCC (pin 40).
42 AM L.C. pin This is because the detector circuit operates referencedto VCC.
The cutoff frequency fC is determined by the followingformula.
fC = 1/2π× 50 kΩ × C
Inserting a 1-MΩ resistor between 43 Pilot detector pin 43 and VCC will force the IC
to mono mode.
No. 6655-15/54
LA1787M
Pin No. Function Description Equivalent circuit
45 IF output The IF amplifier load
+
42
DET
44
VCC
VCC
C2.2µF
0.022µF
50kΩ
50kΩ
240kΩ
G1
10Ω
SEEKON
IFAGC
A13583
45
DET
Pin 40 VCC
Pin 40 VCC
A13584
46
VCC
VCC
50pF
100Ω
20kΩ
ANT DAMPINGDRIVER
W.AGC AMP.
A13585
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G1; Used for time constant switching during seeks.• Receptionτ = 2.2 µF × 300 kΩ
44 IF AGC • Seekτ = 2.2 µF × 10 Ω
The external capacitors are connected to VCC.This is because the IF amplifier operates referenced to VCC.
AM antenna damping I46 = 6 mA (maximum)46 drive output This is the antenna damping
Wide band AGC input current.
No. 6655-16/54
LA1787M
Pin No. Function Description Equivalent circuit
52 IF input The input impedance is 2 kΩ.
47
+–
VCC
30kΩ
R
140µA
Pin 24
MUTE
Inverter
A13586
+
48
+
57
+–
VCC
5.6V 10kΩ
Antennadamping
3.3µF
47µF
For AGC use
A13587
50
51
2.6V
10kΩ 10kΩ
0.022µF 330Ω
IF in
A13588
52
2kΩ
100Ω
A13589
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FM muting on levelModify the value of the external
47adjustment
resistor to adjust the muting onlevel.
RF AGC rectification capacitorThe low frequency distortion isdetermined as follows: Increasing C48 and C57 improves
48 RF AGC bypass the distortion but makes the 57 RF AGC response slower.
Reducing C48 and C57aggravates the distortion but makes the response faster.
50 IF bypass51 FM IF input
Due to the high gain of the limiteramplifer, care must be taken whenchoosing the grounding point forthe limiter amplifer input capacitorto prevent oscillation.
No. 6655-17/54
LA1787M
Pin No. Function Description Equivalent circuit
53
56
IF OUT
IF IN
2.75V
300Ω
VCC
300Ω
A13590
54
49
OSC
Pin 40 VCC
Pin 40 VCC
330Ω
A13591
55
58
+–
W-AGC N-AGC62 pin
VCC
30pF
50pF
50µA
Signal meter
AM SD
C1
C2
MIXIN
MIXOUT
A13592
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• Input and output pin or the firstIF amplifier
• Inverting amplifier
53 IF amplifier output V56 = 2 V56 IF amplifier input Input impedance: RIN = 330 Ω
V53 = 5.3 VOutput impedanceROUT = 330 Ω
The mixer coil connected to the
54 Mixer output: 130 µApin 54 mixer output must be
49 Mixer inputwired to VCC (pin 40).
The pin 49 mixer inputimpedance is 330 Ω
Pins 55 and 58 include built-inDC cut capacitors.The AGC on level is determinedby the values of the capacitorsC1 and C2.
55 W-AGC IN Pin 55 functions as the SDAM SD ADJ sensitivity adjustment pin in
AM mode.58 N-AGC IN
Muting attenuation The output current I55 is 50 µA,adjustment pin and V55 varies depending on the
value of the external resistor. The SD function operates bycomparing V55 with the S-metervoltage.
No. 6655-18/54
LA1787M
Pin No. Function Description Equivalent circuit
59
60
63
O S C
64
1ST.IF
30Ω
VCC
C1
C25pF
5pF
RF AMP
620Ω 620Ω
VCC
A13593
+
3
6 +–
FM.F.EAGC
AM/FMswitching circuit
SD VCC 510Ω
100kΩ3.3V
GNDA13594
8V
62
AM 1stMIX
to RFAmp.
10kΩ
2.1V
A13595
10
10kΩ
5.6V 20pF
33pF
X tal
to 2ndMIX
A13596
Continued from preceding page.
Double balanced mixerPins 59 and 60 are the mixer10.7-MHz output
59Mixer output Pins 63 and 64 are the mixer60
input.This is an emitter insertion typecircuit, and the amount of 63
Mixer input insertion is determined by the64capacitors C1 and C2.
Note:The lines for pins 63 and 64must be kept separated from the lines for pins 59 and 60.
Pin 6 functions both as the FM front end VCC and the AM/FMswitching circuit.
6 Front end VCC AM/FMswitching
1st MIXFirst mixer input
62INPUT
The input impedance is about10 kΩ.
Crystal oscillator circuit10 AM 2nd OSC The Kinseki, Ltd. HC-49/U-S and
a CL of 20 pF must be used.
V6 voltage Mode
When 8 V → FM
OPEN → AM
Block Diagram
No. 6655-19/54
LA1787M
12345678910111213141516
48474645444342414039383736353433
1718
1920
2122
2324
2526
2728
2930
3132
6463
6261
6059
5857
5655
5453
5251
5049
ANTD
BUFFAM1STOSC
AGC
AMPNOISE
PICANINPUT
TRIGGATE
COUNTER
AMP
HPF
FF19k<90k
LPF
SNC
MRC
FF19k<0
FF38k<0
FF
PHASECOMP
VCO
TRIGPILOTDET
P-CAN
SUBDEC
MATRIX
VCOSTOP
MAINHC
HCC
ANTD
HOLEDET
MUTEDRIVE
AMVSMAM SD
IF BUFF
FMVSM
IF limiteramplifier
FM SDDET
IFAGC
BUFF
L.C.
OSCBUFFOSC
DC-CDET
AFCCLAMP
Q.DETMUTEAMP
MIX
AM/FM
MIXRF AGCWB AGC
TWEET
BUFF
AM FMVREFSEEK
SW
SD/STIND
KEYEDAGC
IFREG
AM/FMSW
W.B.AGC
RF AGCAMPINPUT
+
+ –
+
+
+ +
++
+
++
+
+
+
+
+
+
AN
T D
OS
C
RF
AG
C
FE
GN
D
30kΩ
10kΩ
30kΩ
2kΩ
18pF
300p
F
6800pF0.01µF
0.01
5µF
0.01
5µF
0.01µF
0.22µF
0.47µF
1µF
1µF
1µF
AM HC
AM LEVEL 1µ
F
1µF
20kΩ
100kΩ
5.6kΩ
10kΩ
100k
Ω
8200pF
50kΩ
1kΩ
100kΩ
0.047µF
10.2
6MH
z
10pF5pF
25pF
20pF
18pF
1µF
0.02
2µF
0.02
2µF
0.02
2µF
0.01
µF
0.47
µF
1MΩ
+
AM
OS
C
MPXOUT
PI.CAN ADJ
SEP.ADJ
CSB912JF108
AM/FMS-METER
GND
5V
SNC
HCC
NC-IN
DET OUT
METER
FM
GN
D
NC
MP
X G
ND
N.C
.MP
XG
ND
MU
TE
DR
IVE
0.47
µF
0.47
µF
0.22
µF
0.02
2µF
2.2µ
F
3.3µ
F
1µF
11kΩ
IF7
100µ
F
2200
pF
AF
C IN
QD
OU
T
QD
IN
VR
EF
FM
SD
AD
J.
AM
LC
CH
CC
PIL
OT
DE
T
KE
YE
D A
GC10kΩ
10kΩ
30kΩ
240kΩ
6.8k
Ω
0.1µFRFAGC
GND
VCC
0.022µF
0.022µF
0.022µF
100µH
47µF
15pF
15pF
15pF
100µH
0.022µF30Ω
100k
Ω
1kΩ
510kΩ
20kΩ
2.7k
Ω
62pF
330Ω
FC18
ANTD
1MH
30MH
FM IF IN
FM IF OUT
AM IF IN
FE IF IN
0.02
2µF
220Ω
100Ω
AM MIX OUTFM WB AGCIN
AM SD ADJ
MUTE ATT
FEVCC
0.022µF
5pF
5pF
8pF
18pF
30Ω
30Ω
30kΩ
100k
Ω
180Ω 9p
F
39pF
100k
Ω
1000
pF
100k
Ω
100ΩGND
200kΩ
1000
pF
3SK
263
0.1µF
0.022µF
GND
1000pF
1000pF
30kΩ
22pF22pF
0.02
2µF
100k
Ω
VCC
VCC
100F
0.02
2µF
FMIF
AM
GND
FMIF
AM
NC
MPX
VCC
FM
/AM
VS
M
RIG
HT
CH
.
LEF
T C
H.
AM
/FM
OS
C B
UF
F
FM
GN
D
FM
/AM
VT
FM
AN
T IN
AM
RF
GN
D
AM
AN
T IN
AM
VC
C
SE
EK
→A
M/F
M S
DS
TO
P→
FM
ST
IND
.
0.022µFTO
AM
ST
ER
EO
(IF
OU
T)
ADJ
+
+
+
+
+
+
+
+
100k
Ω
100k
Ω
10kΩ
10kΩ
10kΩ
2.2kΩ
0.01
µF
3SK
583
1µF
22pF
22pF
7.2M
Hz
10µF
0.22µF
100p
F
100p
F
100p
F
100p
F
51kΩ
0.22µF
200k
Ω1k
Ω
68pF
2.2k
Ω4.
7kΩ
51kΩ
10µF
10µF
10µF
10µF
240k
Ω
240k
Ω
22kΩ
22kΩ
22kΩ
22kΩ
22kΩ
22kΩ
1kΩ
10kΩ
10kΩ
1kΩ
100k
Ω
100k
Ω1.
5kΩ
100µ
F
100µ
F
5.6V
9.1V
100p
F
CI
CL
DO
RD
S
AD
C
MU
TE
R O
N
SD
/MO
NO
ST
CE
LC86
7148
+B
12V
L
A13
597
R
VS
S
PDVD
D
FM
IN
CI
CL
DO
FM
/AM CE
AM
IN LC72
16M
20191817161514131211
12345678910
AC Characteristics Test Circuit
No. 6655-20/54
LA1787M
12
34
56
78
910
1112
1314
1516
4847
4645
4443
4241
4039
3837
3635
3433
17181920212223242526272829303132
64636261605958575655545352515049
AN
TD
BU
FF
AM
1ST
OS
C
AG
CT
RIG
GA
TE
HP
F
FF
19<
90 k
LPF
SN
C
MR
C
FF
19<
0
F
F38
k<0
FF
PH
AS
EC
OM
P
VC
O
TR
IGP
ILO
TD
ET
P-C
AN
SU
BD
EC
MA
TR
IX
VC
OS
TO
P
MA
INH
C
HC
C
AN
TD
HO
LED
ET
MU
TE
DR
IVE
AM
VS
MA
M S
D IF B
UF
FFM
VS
MF
M S
DD
ET
IFA
GC
BU
FF
L.C
.
OS
CB
UF
FO
SC
DC
-CD
ET
AF
CC
IAM
P
Q.D
ET
MU
TE
AM
P
MIX
AM
/FM
MIX
RF
AG
CW
.B. A
GC
TW
EE
T
BU
FF
AM
FM
VR
EF
KE
YE
DA
GC
FF
RE
GF
M/A
MS
W
W.B
.AG
C
RF
AG
C
+
+–
+
+
++
++
+ ++
+
+
+
+ +
ANT D
RF AGC
FE GND
OS
C
20kΩ
SW
1
VA
1V
A9
8V
VC
C
VA
6
10kΩ
20pF
300pF
6800
pF0.
01µF
10µF
0.015µF
0.015µF
0.01
µF
0.22
µF
0.47
µF
1µF
BA
SW
4 (T
)
1µF
AM
HC
AM
LE
VE
L
1µF 1µF
20kΩ
20kΩ
3pF
100k
Ω
VR
1
VR
2
8VS
W9
5.6k
Ω
8200
pF
0.04
7µF
0.02
2µF
10.2
6MH
zX
TA
L
5pF
25pF 20pF
1µF
0.022µF 0.022µF
0.01µF
0.47µF
1MΩ
50kΩ
50kΩ
VD
2
VA
3
FM
/AM
IFB
UF
F.V
D4
SW
5
4.3k
Ω
100kΩ
100kΩ
+
AM
OS
CM
PX
OU
T
PI.C
AN
AD
J
SE
P.
AD
J
CS
B91
2JF
108
AM
/FM
S-M
ET
ER
GN
D
SN
C
HC
C
NC
-IN
DE
T O
UT
FM
S-M
ET
ER
N.C.MPX GND
MU
TE
DR
IVE
0.1µF
0.47µF
0.22µF
0.022µF
2.2µF
3.3µF
1µF
15kΩ
180kΩ
IF7
100µF
2200pF
AFC IN
QD OUT
QD IN
VREF
FM SD ADJ.
AM LC
CHCC
PILOT DET
MUTE OR ADJ
KEYED AGC
10kΩ
10kΩ
22kΩ
240k
Ω
6.8kΩ
0.1µ
FR
FA
GC
IF O
UT
B A
IF IN
SW
3
SW
2 (
i )M
IX
GN
D
VC
C
0.02
2µF
0.022µF
100µ
H
47µF
20kΩ
0.022µF
100µ
H
0.02
2µF
30Ω 100kΩ
1.6k
Ω
510Ω
30Ω
25Ω
50Ω
10pF
330Ω
FC
18
AN
TD
VD
6
SW
8S
W7
1mH
6.8mH
FM
IFIN
FM
IF O
UT
AM
IF IN
FE
IF IN
330Ω
200Ω
0.02
2µF
18pF
AM
MIX
OU
T
FM
WB
AG
CIN
AM
SD
AD
J
MU
TE
AT
T
FE
VC
CV
CC
5pF
5pF
3pF
39pF 100kΩ
50Ω
10kΩ
1MΩ
100Ω
100Ω
GN
D
VT
0.02
2µF
0.02
2µF
1000
µF
0.02
2µF
15pF
JIS
DU
MM
Y
30Ω
50Ω
65pF
30kΩ
RIGHT CH.
LEFT CH.
AM/FM OSC BUFF
VA
2
FM GND
FM VCC
SE
EK
→A
M/F
M S
DS
TO
P→
AM
ST
BU
FF
ER
F
M S
T IN
D.
AD
J
VD
1
200kΩ
30kΩ
VC
C2
VD
3
VC
C2
VD
5
MR
C-I
N
VC
C8V
VC
C3
HC
C
NC
-IN
SN
C
PG
1(A
C1)
+
VC
C1
5V
100kΩ
SW
6
+
+
AC
5
+
AC
1S
G1
300Ω
50Ω
50Ω
+
AC
3S
G3
+
AC
2S
G2
A13
598
3pF
0.02
2µF
10kΩ
10kΩ
VC
C
VA
7
8VS
W10
10µF
+
10kΩ
1MΩ
VA
8
IF li
mite
ram
plifi
er
No. 6655-21/54
LA1787M
Parameter SymbolSwitch states
SW1 SW2 SW3 SW4 SW5 SW6 SW7 SW8 SW9 SW10
Current drain ICCO-FM ON b OFF b — ON OFF OFF ON —
Demodulation output VO-FM ON b OFF b — ON OFF OFF ON —
Pin 31 demodulation output VO-FM31 ON b OFF b — ON OFF OFF ON —
Channel balance CB ON b OFF b — ON OFF OFF ON —
Total harmonic distortion (FM) THD-FMmono ON b OFF b — ON OFF OFF ON —
Signal-to-noise ratio: IF S/N-FM IF ON b OFF b — ON OFF OFF ON —
AM suppression ratio: IF AMR IF ON b OFF b — ON OFF OFF ON —
Att-1 ON b OFF b — ON OFF OFF ON —
Muting attenuation Att-2 ON b OFF b — ON OFF OFF ON —
Att-3 ON b OFF b — ON OFF OFF ON —
Separation Separation ON b OFF b — ON OFF OFF ON —
Stereo on level ST-ON ON b OFF b — ON OFF OFF ON —
Stereo off level ST-OFF ON b OFF b — ON OFF OFF ON —
Main total harmonic distortion THD-Main L ON b OFF b — ON OFF OFF ON —
Pilot cancellation PCAN ON b OFF b — ON OFF OFF OFF/ON —
SNC output attenuation AttSNC ON b OFF b — ON OFF OFF ON —
HCC output attenuation 1 AttHCC-1 ON b OFF b — ON OFF OFF ON —
HCC output attenuation 2 AttHCC-2 ON b OFF b — ON OFF OFF ON —
Input limiting voltage Vi-lim ON b OFF b — ON OFF OFF ON ON
Muting sensitivity Vi-mute ON b OFF b — ON OFF OFF ON —
SD sensitivity 1 SD-sen1 FM ON b OFF b OFF OFF OFF OFF ON —
SD sensitivity 2 SD-sen2 FM ON b OFF b ON OFF OFF OFF ON —
IF counter buffer output VIFBUFF-FM ON b OFF b OFF OFF OFF OFF ON —
VSM FM-1 ON b OFF b — ON OFF OFF ON —
Signal meter output (FM)VSM FM-2 ON b OFF b — ON OFF OFF ON —
VSM FM-3 ON b OFF b — ON OFF OFF ON —
VSM FM-4 ON b OFF b — ON OFF OFF ON —
Muting bandwidth BW-mute ON b OFF b — ON OFF OFF ON —
Mute drive output VMUTE-100 ON b OFF b — ON OFF OFF ON —
N-AGC on input VNAGC ON a ON b — ON OFF OFF — —
W-AGC on input VWAGC ON a ON b — ON OFF OFF — —
Conversion gain A.V ON a ON b — ON OFF OFF — —
Oscillator buffer output VOSCBUFFFM ON a ON b — ON OFF OFF — —
Gate time 1 τGATE1 ON — OFF a — ON OFF OFF — —
Noise sensitivity SN ON — OFF a — ON OFF OFF — —
NC effect SN-NC ON/OFF — OFF a — ON OFF OFF — —
MRC output VMRC ON — OFF b — ON OFF OFF — —
MRC operating level MRC-ON ON — OFF b — ON OFF OFF — —
Practical sensitivity S/N-30 OFF — OFF b ON ON — — — —
Detection output VO-AM OFF — OFF b ON ON — — — —
Pin 31 detection output VO-AM31 OFF — OFF b ON ON — — — —
AGC F.O.M. VAGC-FOM OFF — OFF b ON ON — — — —
Signal-to-noise ratio S/N-AM OFF — OFF b ON ON — — — —
Total harmonic distortion (AM) THD-AM OFF — OFF b ON ON — — — —
Signal meter output (AM)VSM AM-1 OFF — OFF b ON ON — — — —
VSM AM-2 OFF — OFF b ON ON — — — —
Oscillator buffer output VOSCBUFF AM-1 OFF — OFF b ON ON — — — —
Wide band AGC sensitivityW-AGCsen 1 OFF — OFF b ON ON — — — —
W-AGCsen 2 OFF — OFF b ON ON — — — —
SD sensitivitySD-sen1 AM OFF — OFF b OFF OFF — — — —
SD-sen2 AM OFF — OFF b OFF OFF — — — —
IF buffer output VIFBUFF-AM OFF — OFF b OFF OFF — — — —
Test Conditions
Usage Notes
1. Notes on VCC and Ground
* : When applying the VCC voltage to pin 6, that voltage must not exceed the pin 40 and pin 61 VCC voltages.(This condition must be checked carefully when first applying the pin 6 voltage.)
2. Notes on AM Coil ConnectionThe VCC used for the first oscillator coil connected to pin 7 must be at the same potential as pin 61.Connect to the IFT connected with pin 45, and to the MIX coil connected with pin 54. VCC must be at the same potentialas pin 40.
3. AM/FM SwitchingPin 6 is also used as the FM front end and RF AGC VCC
No. 6655-22/54
LA1787M
Pin 40 VCC for the FM IF, AM, NC, MPX, and MRC blocks
Pin 25 Ground for the FM IF and AM blocks
Pin 14 Ground for the NC, MPX, and MRC blocks
Pin 61 VCC for the FM front end, AM first mixer, and first oscillator blocks
* Pin 6 VCC for the FM front end and AGC blocks, and the AM/FM switching pin
Pin 3 Ground for the FM front end, first mixer, and first oscillator blocks
Pin 6 voltage Mode
8 FM
OPEN AM
Fig. 1
LA1787M Overview
1. Notes on the LA1781M, LA1784M, and LA1787M
The LA1784M is a version of the LA1781M that uses an external oscillator circuit, and has the same characteristics asthe LA1781M.The LA1787M is a version of the LA1784M that features improved characteristics.
LA1781M LA1784M LA1787M
This product is a version of the LA1781Mwith the oscillator circuit removed. Itsupports the use of an external oscillatorcircuit.It has the same characteristics as theLA1781M.
The LA1787M features improvedcharacteristics over the LA1781Mand LA1784M.
No. 6655-23/54
LA1787M
2. Modified circuits
The following characteristics have been improved over those of the The LA1784M.
• The AM adjacent channel interference characteristics (∆40 kHz) have been improved.• The AM S-meter curve slope has been increased.• The FM separation temperature characteristics have been improved.• The stereo indicator sensitivity has been improved.• The FM oscillator circuit has been omitted.
(1) AM interference characteristics improvement
The second signal interference and suppression have been improved for adjacent channels (±40 kHz) by increasingthe AM second mixer input dynamic range.
(2) The AM S-meter curve slope has been increased.
The slope of the AM S-Meter curve has been increased from that of the LA1781M and LA1784M.
–20 00
2
3
4
5
6
7
1
20 40 60 80 100 120 140
LA1787MLA1780M
LA1781M
AM S-Meter Voltage
Antenna input — dBµ
S-m
eter
vol
tage
— V
(3) FM separation temperature characteristics improvement
The temperature characteristics have been improved, the amount of change in the separation due to drift when atpower on has been stabilized. This makes it easier to adjust the separation.
35
40
45
50
55
60
0 1 2 335
40
45
50
55
60
0 1 2 3
Change in Separation (LA1781M): First IF Input
Time after power on — minutes
Cha
nge
in s
epar
atio
n —
dB
Change in Separation (LA1787M): First IF Input
Time after power on — minutes
Cha
nge
in s
epar
atio
n —
dB
No. 6655-24/54
LA1787M
(4) Stereo indicator sensitivity improvement
The stereo indicator sensitivity (on/off) is equivalent to that of the LA1780M
Stereo on level Stereo off level
LA1781M/1784M 4.1% 3.1%
LA1787M/1780M 2.6% 1.6%
* : The pilot level such that the stereo indicator goes on or off for a 10.7 MHz unmodulated IF input.
(5) FM oscillator circuit removed
The internal FM oscillator circuit provided in the LA1781M has been removed. The FM oscillator level can beadjusted by constructing an external circuit block.
*: However, this requires 4 more external parts than the LA1781M: 1 transistor and 3 resistors/capacitors.
4
Vt
VCCVCC
A13600
4
Vt
VCC
IC internalIC internal
A13601
LA1787M/1784M FM OSC LA1780M/1781M FM OSC
3. Gain distribution
The table below shows the gain distribution of the LA1780M, LA1784M, and LA1787M. (These are measuredvalues.) Compared to the LA1784M, the total gain is lower.
1st MIX (10.7) 1st IF (10.7) 2nd MIX (450) 2nd IF (450)
LA1780M 10 dB 3.3 dB 3.2 dB 69 dB
LA1784M 7.5 dB 13 dB 7 dB 66 dB
LA1787M 7.5 dB 3.5 dB 8.6 dB 67 dB
First mixer : No circuit changes from the LA1784M.
First IF amplifier : Equivalent to the LA1780M circuit. (The gain is lower than that in the LA1781M and LA1784M.)
Second mixer : The mixer circuit has been modified to improve adjacent channel suppression and interference.
Second IF amplifier : Equivalent to the LA1780M circuit.
(Typical value)
No. 6655-25/54
LA1787M
4. Changes to applications
Component values that change from LA1781M/LA1784M applications(Since the total AM gain has changed in the LA1787M)
• AM SD adjustment resistor (pin 55): Because Vsm is higher.• AM level adjustment resistor (pin 31):Since the post-detection audio amplifier gain is higher than in the LA1781M
and LA1784M, the output level is also higher. This resistor must be changedto match the set value.
• AM mixer coil (pin 54), IFT coil (pin 45) damp resistor:Since the IF block gain is increased, the mixer (pin 54) andIFT (pin 45) coil damping must be adjusted.
• Separation adjustment resistor (pin 19):Since an internal 4 kΩ resistor has been added to the pin 19 input circuit toimprove the separation temperature characteristics, the value of the externalresistor must be reduced from that used with the LA1780M, LA1781M, andLA1784M. (See the following page.)
19
30kΩ
0.047µF
DECODERComposite Sign
19
30kΩ
Added 4 kΩ resistor
5kΩ
0.047µF
DECODERComposite Sign5kΩ
A13602 A13603
LA1781M/1784M LA1787M
1. Notes on the FM Front EndNotes on interference rejection characteristics
• Intermodulation characteristicsThe LA1787M applies two high-band AGC functions to prevent IM (the generation of intermodulation). These arethe narrow AGC (pin 58: mixer input detection type) and the wide AGC (for the pin 55 input), and this results in theantenna frequency characteristics shown in figure 2. The levels at which the AGC functions turn on are determinedby the capacitors attached at pins 55 and 58.
–4–5 –2–3 –1 050
70
80
90
100
110
60
1 2 3 4 5
When ∆f = 0, 98.1 MHz
The wide AGC sensitivity when pin 39 is 5 V.
AG
C s
ensi
tivity
— d
Bµ
∆f — MHz
∆f — AGC Sensitivity
The narrow AGC sensitivity when pin 39 is at ground.
Fig. 2
Functions
No. 6655-26/54
LA1787M
• Notes on second-channel attenuation suppressionKeyed AGC (3D AGC) is a technique for achieving good characteristics for both intermodulation and second-channel attenuation at the same time. When the desired signal is faint or nonexistent, the high-band AGC level willbe essentially 0, and as a result automatic tuning may malfunction and blocking oscillation may occur in thepresence of strong interfering stations. Keyed AGC helps resolve these problems.This 3D AGC technique uses information that has the following three frequency characteristics and is a uniqueSanyo-developed system for determining the high-band AGC level.
RF and ANT circuit information: Mixer input AGCMixer circuit information: Mixer output AGCCF selectivity information: S-meter output
–4–5 –2–3 –1 050
70
80
90
100
110
60
1 2 3 4 5
Pin 58 capacitor: 10 pF
Nar
row
AG
C o
n le
vel —
dB
µ
∆f — MHz
∆f — AGC on Level (ANT input)
Pin 58 capacitor: 47 pF
39
keyed AGC
Fig.3
140
130
120
110
100
90
80
70
7 1.0 2 3 5 7 10 2 3 5 7 100 2 3 5
Wide AGC on level frequency characteristics
Narrow AGC on level frequency characteristics
AGC input level frequency characteristics such that VRFAGC (pin 2) falls under 2 V.
Pin
59 n
arro
w A
GC
and
pin
55 w
ide A
GC
inpu
t lev
els —
dBµ
Frequency, f — MHz
W-AGC, N-AGC — f Fig.5
–4–5 –2–3 –1 050
60
70
80
90
100
110
1 2 3 4 5
Pin 55 capacitor: 3 pF
Pin 55 capacitor: 10 pF
Wid
e A
GC
on
leve
l — d
Bµ
∆f — MHz
∆f — AGC on Level (ANT input)
39
5V
keyed AGC
Fig.4
• 3D AGC Features
Feature Merit
Only the narrow AGC sensitivity (operation at ∆f < 1.5 MHz) is • Effective in resolving second-channel attenuation problems.controlled by the field strength of the desired station.
The narrow AGC sensitivity is controlled by a voltage (V23) that is • Allows effective resolution of second-channel attenuation problems without under 0.5 V. degrading three-signal characteristics.
• Seek operations may stop incorrectly due to the occurrence of
The wide AGC can operate even when V23 = 0 (when the desired intermodulation.
station is not present).• It is possible to prevent the occurrence of intermodulation in the RF tuning
circuit and antenna in the presence of strong interfering stations, and blocking oscillation due to AGC operation can be prevented.
The narrow and wide AGC sensitivities can be set independently.• Settings can be optimized for the field conditions.(See figure 3 and 4.)
The system has two AGC systems: narrow and wide AGC. • Since the narrow AGC operates for the desired station and adjacent
(See figure 5.)stations, the wide AGC sensitivity can be lowered and AGC malfunction due to local oscillator signal can be prevented.
3D AGC Sensitivity Characteristics
No. 6655-27/54
LA1787M
Second-channel attenuation improvement
Desired station AGC sensitivity
4
3
2
1
∆F
Narrow AGC sensitivity
V23 (Desired station field strength)
Wide AGC sensitivityAGC sensitivity
A12075
3D AGC Sensitivity — ∆f, V23 characteristics• The wide AGC sensitivity is determined by the antenna and RF circuit selectivity, regardless of V23.• The narrow AGC sensitivity is determined by the following.
The total selectivity of the antenna, RF circuit, and mixer when V23 ≥ 0.5 VThe above selectivity and V23 when V23 < 0.5 V
• The improvement in the second-channel attenuation corresponds to the area occupied by the narrow AGC in thetotal AGC sensitivity area.Figure 8 on the next page shows the actual operation of the circuit.
–4–5 –2–3 –1 050
60
70
80
90
100
110
1 2 3 4 5
The f
u in
put l
evel
at wh
ich an
tenna
dam
ping
turn
s on
— d
Bµ
∆f — MHz
∆f — AGC on Level (ANT input)
A12076
ANT INVIN
Second-channel padfD = 98.1 MHz
fu = 98.1 MHz + ∆f
Fig. 6
Fig. 7
Notes on 3D AGC (Keyed AGC)
• The antenna damping current from the pin due to the pin diode flows when the V2 pin reaches the VCC - VBElevel.
• The narrow AGC operates as follows.When pin V39 > pin V24: The narrow AGC turns off.When pin V39 < pin V24: The narrow AGC turns on.
No. 6655-28/54
LA1787M
+
55W-AGC
DET
58
1 2 39 24
N-AGCDET
+
–
+
–
VCC
VCC
ANTDUMPING
90µA S-meter
VS-meter
A11763
Fig. 8
• The LA1787M includes two AGC circuits in its front end block.— Antenna input limiter using a pin diode.— FET second gate controlThe AGC input pin is pin 59, and the AGC circuit turns on when a signal of about 30 mVrms is input.
AGC activationThe pin diode drive circuit turns on when VCC – V2 is greater than or equal to about 1 V, and input limitation isapplied to the antenna circuit. In application circuits, there will be an attenuation of about 30 to 40 dB. Next, whenan adequate current flows in the antenna attenuator pin diode, the inductance falls, the FET second gate voltagedrops, the FET gm falls, and the AGC operates. The recommended FET is the Sanyo 3SK263, which is anenhancement-type MOSFET. Therefore, full AGC is applied when the voltage, VG2-S, between the second gate andthe source is 0. Note that if a depletion-type MOSFET is used, AGC will not be applied unless VG2-Sis less than 0.
No. 6655-29/54
LA1787M
0
1
2
3
4
5
6
7
8
9
–10 0 10 20 30 40 50 60 70 80 90 100 110 120 130 140
fr = 98.0 HzVCC = 8 VTa = 25°C
Range where the AGC does not operate
AGC level due to the MOSFET second gate: about 35 dB
AGC level due to the pin diode: about 35 dB
V2A
GC
—
V
ANT IN — dBµ
V2 AGC Characteristics Fig.9
5964 60 63 62
OSC
A12077
MIX
INP
UT
MIX
OU
T
MIX
OU
T
MIX
INP
UT
MIX
VC
C
MIX
Mixer circuit
• MixerThe mixer circuit in this IC is a double-balanced mixer with bothbalanced input and balanced output.Input circuit typeEmitter inputInput impedance: 25 Ω
Due to optimized device geometry, emitter current, the bias, this ICachieves the following performance.
Mixer input usable sensitivity: 15 dBµMixer input IMQS: 90.5 dBµ(For an oscillator level of 200 mVrms)
* The mixer input IMQS is defined as:
fr = 98.8 MHz, no inputfu1 = 98.8 MHz, 1 kHz, 30% modulationfu2 = 99.6 MHz, no modulation
The interference 1 and 2input levels such thatgenerated intermodulationoutput signal-to-noise ratiobecomes 30 dB when aninterference signal with thesame level as the mixer inputis input, and distortion occursin the mixer.
Fig. 10
• OscillatorFigure 11 shows the type of oscillator circuit used in this IC. It includes both an oscillator and an oscillator buffer.
No. 6655-30/54
LA1787M
5
4
VT
18pF
25pF
20pF
VCC
AM/FMOSC BUFFER OUT
A12078
56 53
+
–
TO MIX
330Ω
330Ω
330Ω
FM IF input
A12079
• Figure 12 shows the type of FM first IF amplifier used in this IC. It is a differential single-stage amplifier.
SpecificationsInput impedance: 330 ΩOutput impedance: 330 ΩGain: 20 dB
Fig. 11
Fig. 12
2. FM IF• Notes on the FM SD and SD adjustment
The figure below presents an overview of the FM SD and the IF count buffer.
No. 6655-31/54
LA1787M
S-meter
FM IF
HOLECLET
Mutingdrive
outputSTEREO
IND
Bandmuting
39 24 33 23 26
+
–
+
–
+
–
4.9V R
R
R
IF count buffer
IF count output
2.5V 5V
SDSTEREO/MONO
5V
A11759
V23DC
V23AC
V26
V33
V38
V24
5 V
Larger values of R33
Smaller values of R33
S-meter
V33 over 0.7 V
V33 over 0.7 V
On as anSD signal
SDON
SDON Stereo
Mono
0.7 V
OFF OFFIF countbuffer
5 V
2.5 V 0 V
IF counter output off
RDS and other types of SD detection can be used by switching these modes.
A11758
For stereo input (when the V26 pin voltage is 0.7 V), when this pin is shorted to ground (0.1 V or lower) the IC will operate in forced mono mode.
New LA1784M functionality:
Fig. 13
Fig. 14
Figure 14 shows the relationship between the FM SD, the IF count buffer output, the S-meter, and the muting driveoutput.
• Transient response characteristics during automatic tuningThe transient characteristics for SD and IF count buffer on/off operation are determined by the time constants ofthe RC circuits attached to the following pins.(1) Muting time constant: pin 33(2) S-meter time constant: pin 24(3) AFC time constant: pin 34
There are two points that require consideration when using fast tuning.(1) The SD time constant due to the S-meter time constant
Since the current I24 (pin 24) varies with the field strength, the time constant also changes. There is no hysteresisin the comparator.If a smaller value is used for C24, you must select a value for C such that the AGC does not become unstablewhen the pin 24 voltage is used for keyed AGC.
(2) The SD time constant due to the pin 33 muting voltage time constantThe changes in volume due to field fluctuation during weak field reception can be made smoother by setting theattack and release times during soft muting operation.
No. 6655-32/54
LA1787M
24
S-meter
C24
A12080
10k
Muteamp
Mutedrive
10kΩ 50kΩ
C33
A11766
33
Attack Release
0
10
20
30
40
50
6 10 14 18 22 26 30 34
Ant
enna
inpu
t suc
h th
at p
in 5
goe
s hi
gh —
dB
µ
Resistance between the pin and ground — kΩ
SD Sensitivity Adjustment Fig.17
Fig. 15
Fig. 16
Muting time constants
Attack: 10 kΩ × C33
Release: 50 kΩ × C33
However, when testing this stop sensitivity, note that when checking the waveform on the IF count buffer output(pin 23), there are cases, such as that shown below, where current in the test system may be seen as flowing toground and cause oscillation that causes the IF count buffer output to go to the output state.
• FM Muting control pin (pin 47) (R47: 30 kΩ variable resistor)The –3 dB limiting sensitivity can be adjusted with R47.
• FM muting attenuation adjustment (pin 58)The muting attenuation can be switched between the three levels of –20, –30, and –40 dB by the resistor insertedbetween pin 58 and ground. (Note that the exact values depend on the total tuner gain.)The noise convergence with no input is determined by the pin 58 voltage.
The attenuation can be set by making R33 smaller as listedin the table above.
No. 6655-33/54
LA1787M
IF bufferampIFF.E.
5 V 0.022 µF
The 10.7 MHz feeds back through ground.
Test system capacitance
A12081
FM Soft Muting (1)
Antenna input — dBµ
Out
put n
oise
— d
B
DET out
Noise
15 kΩ
10 kΩ
20 kΩ
R47 = 7.5 kΩ
Fig.19
58
100Ω R58
A11764
R33
A11765
33
Fig. 18
Fig. 20
R58 Mute ATT
Open –20 dB
200 kΩ –30 dB
30 kΩ –40 dB
Out
put,
nois
e —
dB
No. 6655-34/54
LA1787M
FM Soft Muting (2) FM Soft Muting (3)
Antenna input — dBµ Antenna input — dBµ
Out
put n
oise
— d
BO
utpu
t —
dB
Out
put
— d
B
10 kΩ
10 kΩ
20 kΩ
2 0kΩ
15 kΩ
15 kΩ
DET out DET out
Noise Noise
R47 = 7.5 kΩR47 = 7.5 kΩ
Fig.21 Fig.22
200 kΩ
30 kΩ
+
–
+
–
58 33 31
200 kΩ R
VCC
R
R
N-AGC
To MIX out
Open
200 kΩ 30 kΩ
Mutedrive
Limiter
Quadrature detector Mute amp.(VCA)
DET out
A11767
20
1
0Detector output
Antenna input
When the pin is at the ground level, the noise convergence will be 10 dB and the –3 dB limiting sensitivity will be about 0 dBµ.
A12082
• FM muting off functionForcing this pin to the ground level turns muting off.
Fig. 23
Fig. 24
Out
put,
nois
e —
dB
• Hall detectionThe Hall detection function detects the level of the pin 36 quadrature input signal and then applies peak detectionto that result. The result is output from pin 33. This circuit has three effects.(1) It assures that muting will be applied for weak inputs with an antenna input of under 5 dBµ. The amount of
attenuation is referenced to an antenna input of 60 dBµ, fm = 1 kHz, and a 22.5 kHz dev output, and is variablefrom 10 dB to 40 dB when there is no input. Thus one feature of this circuit is that the weak input noiseattenuation and the –3 dB limiting sensitivity for over 5 dBµ inputs can be set independently.
(2) When the pin 36 quadrature input is a saturated input, the pin 36 noise level (Va) is detected and a peak-holdfunction is applied to pin 33 (Vb) for locations rapid field strength variations and severe multipath occurs forfields that result in an antenna input level of over 5 dBµ.
(3) Unique featuresOne unique feature of the LA1784M is that if there are adjacent stations such that f1 = 98.1 MHz and f2 = 97.9 MHz, a search operation will not stop at 98.0 MHz. Since VAFC = 0 V and VSM = 3.6 V at 98.0 MHz inthe situations shown in figure 27 and 28, even though Hall detection would normally not operate and SD wouldbe high, in this IC the Hall detection circuit will operate, VMute will be set to 1.2 V (over 0.7 V) and the SDsignal will go low, thus preventing incorrect stopping of the search.
No. 6655-35/54
LA1787M
0
1
2
3
4
5
–20 –10 0 10 20 30
Area muted by Hall detection
V38
pin
—
V
Antenna input — dBµ
Hall Detection Output — Antenna Input Characteristics Fig.25
36
33
+
0 0
0.1µFVaVb
A12083
Fig. 26
No. 6655-36/54
LA1787M
0
2
4
6
8
0
2
4
6
0
2
4
6
–1
0
1
2
97.7 97.8 97.9 98.0 98.1 98.2 98.3
f2 = 97.9 MHz, 120 dBµfm = 400 Hz, 22.5 kHz dev.
When the tuner is moved in 50 kHz steps.With a 51 kΩ resistor between pins 37 and 34.With the SD sensitivity adjusted to be 20 dBµ.
f1 = 98.1 MHz, 120 dBµfm = 1 kHz, 22. 5kHz dev.
Pin
26 (
SD)
— V
Pin
24, V
SM —
VPi
n 33
, VM
ute
— V
Vol
tage
bet
wee
n pi
ns 3
7 an
d 34
, VA
FC —
V
Frequency, fr — MHz
Unique Features of the LA1784M Hall Detection Circuit (1)
f1
f2
ANTIN
Fig.27
0
2
4
6
8
0
2
4
6
0
2
4
6
–1
0
1
2
97.7 97.8 97.9 98.0 98.1 98.2 98.3
f2 = 97.9 MHz, 40 dBµfm = 400 Hz, 22.5 kHz dev.
When the tuner is moved in 50 kHz steps.With a 51 kΩ resistor between pins 37 and 34.With the SD sensitivity adjusted to be 20 dBµ.
f1 = 98.1 MHz, 40 dBµfm = 1 kHz, 22.5 kHz dev.
Pin
26 (
SD)
— V
Pin
24, V
SM —
VPi
n 33
, VM
ute
— V
Vol
tage
bet
wee
n pi
ns 3
7 an
d 34
, VA
FC —
V
Frequency, fr — MHz
Unique Features of the LA1784M Hall Detection Circuit (2) Fig.28
• Notes on the quadrature input levelWhen a strong field is being received the quadrature signal input (pin 36) requires a 200 mV rms input, and thedetection transformer and the damping resistor between pins 36 and 37 must be designed.(We recommend the Sumida SA-208 transformer and a 10 kΩ resistor between pins 36 and 37.)When the pin 36 input level falls below 160 mV rms, the Hall detection circuit operates and the pin 33 mute driveoutput voltage increases. Therefore, when pin 36 input is from 160 to under 200 mV rms during strong fieldreception, the muting circuit may or may not operate due to sample-to-sample variations between individual ICs.Furthermore, the SD function may not operate, and the audio output level may be reduced. Incorrect operation dueto sample-to-sample variations and temperature characteristics can be prevented by keeping the pin 36 voltage at200 mVrms or higher.
0
1
2
3
4
5
6
92 94 96 98 100 102 104 106
With pins 34 and 37 shorted.With 5 V applied to pin 24.
Vm
ute
—
V
QD input level — dBµ
Pin 33 VMute — QD Input Level
36 37
SG
10.7 MHz LA1888M
75 Ω 75 Ω+
0.022 µF
Fig.29
–0.8
–0.6
–0.4
–0.2
0.2
0.4
0.6
0.8
1
2
3
4
–100 –80 –60 –40 –20 0 20 40 60 80 100 120–120
With the resistor between pins 36 and 37 open.
∆f — kHz
∆f=0→ 10.7 MHzWith a 10 kΩ resistor
between pins 36 and 37.
Voltage between pins 37 and 34 (referenced to the pin 37 voltage)
THD 1 kHz75 kHz dev
SA208 + LA1787M IF Input Characteristics
TH
D
—
%
Fig.30
No. 6655-37/54
LA1787M
Detector output Pin 36 AC levelMPX OUT
R36-37 Vo QDIN
Open 330 mVrms 235 mVrms
10 kΩ 280 mVrms 200 mVrms
• Band Muting Adjustment ProcedureThe muting bandwidth can be modified as shown in figure 31 with the resistor RBW between pin 34 and 37.
3. AM• AM AGC system
The LA1787M RF AGC circuit takes its input from three sources: the WIDE AGC pin (pin 46), the MIDDLEAGC pin (pin 49) and NARROW AGC. There is also an IF AGC circuit.
0
40
80
120
160
200
240
280
1.0 2 3 5 7 10 2 3 5 1007 2
SA208Sumida
Band
wid
th su
ch th
at th
e pin
33
volta
ge ≥
2 V
— k
Hz
Resistor RBW between pins 34 and 37 — kΩ
37 36 35 34
+ +
1 µF 0.47 µF
10 kΩ
RBW
ANT IN 98 MHz 100 dBµ
Fig.31RBW — Muting Bandwidth
+
62
46
57
49RF 52 31
+
48
44
42
RW
1st MIX 10.7MHz CF 2nd MIX 450kHz CF IF Amp. DET
1st OSC X'tal
Middle AGC INNarrow AGC IN
Wide AGC IN
ANTdamping
RF AGC
47 µF 3.3 µF
Amp. IF AGC2.2 µF
240 kΩ
VCC
VCC
A11762
Fig. 32
No. 6655-38/54
LA1787M
800 900 100060
80
70
90
100
1100 1200
AG
C o
n le
vel
Frequency — Hz
AM AGC f characteristics
Wide AGCOperates for wide band interference
Wide AGCOperates for wide band interference
Middle AGCOperates for interference within ±70 kHz of the received frequency.
Middle AGCOperates for interference within ±70 kHz of the received frequency.
Narrow AGCOperates at the received frequency.
Fig.33
70
80
90
100
110
120
21.0 3 5 7 10 2 3 5
Received frequency: 1 MHz
Ant
enna
dam
ping
on
inpu
t lev
el —
dB
µ
Pin 46 input — MHz
Wide Band AGC Circuit
30 Ω 0.022 µF
0.022 µF
0.022 µF
4650 Ω
510 Ω
50 Ω
–6dB
SG
ANTD
Fig.34
62
57
+
VCC
0.022 µF30 Ω
620 Ω 1MH
100 µH
100 µH
30M
H
15 p
F
15 p
F
47 µ
F
100
kΩ
0.02
2 µF
Wide band AGC adjustment resistor
A12084
FC18
The wide band AGC circuit in this IC has the frequency characteristics shown above. The pin 46 input frequencycharacteristics are identical to those of the RF amplifier gate. This AGC circuit serves to prevent distortion at theFET input when a strong signal is applied to the antenna circuit. The level at which the AGC circuit turns on can beadjusted to an arbitrary level with the wide band AGC adjustment resistor. A delayed AGC on level can be handledby reducing the value of the adjustment resistor.
Fig. 35
• Notes on AM SD (pin 26) and the SD adjustment pinSD and the IF buffer are operated by comparing the S-meter level (V24) and the 5 V reference voltage as shown infigure 36.
Figure 37 shows the relationship between the AM SD, the IF count buffer, and the S-meter.
No. 6655-39/54
LA1787M
55 24 23 26
AM IF
+
–
S-meter
100 kΩ0.47 µF
51 kΩ
Seek
5 V
5 V
IF buffer
IF buff amp.
SD
0.022 µF
100 kΩ
50 pF
Comparator
50 µA
VCC
A12085
V23DC
V23AC
V26
V55
V24PIN
Larger values of R55
Smaller values of R55
5 VPin 55: AM SD adjustment pin
OFF IF buffer on
SD on
S-meter
0 V
A11760
Fig. 36
Fig. 37
• AM high band cut and detector output level adjustment methodsThe pin 31 AM and FM tuner output has an impedance of 10 kΩ in AM mode and a few tens of Ohms in FMmode. Therefore, R31 is used to lower the AM detector output level and C31 determines the AM high bandfrequency characteristics.
• AM stereo system pins
No. 6655-40/54
LA1787M
Fig. 39
31
30
+
FMdetector
AMdetector
VCC
VCC
10 kΩ
Noise canceler input
50 kΩ
R31 C31
A12086
45 39
VCC
VCC
IFT
50 pF 150 Ω
IF AMP.
Keyed AGC
GND
To the AM stereo decoder
400 mV rms 450 kHz output
A11761Fig. 40
No. 6655-41/54
LA1787M
• AM low band cut adjustment methodThe AM low band frequency characteristics can be adjusted with C42, which is inserted between pin 42 and VCC.Since the detector is designed with VCC as the reference, C42 must be connected to VCC.
AMdetector
42
+
–
50 kΩ
50 kΩ
10 kΩ10 kΩ
10 kΩ
C42
VCC
To pin 31
A12087
–40
–30
–20
–10
0
10
3 5 70.010.001 2 3 5 72 3 5 72 3 5 720.1 1.0 10
0.043 µF (41pin)% with no used (31pin)
0.022 µF (41pin)With no used (31pin)
0.022 µF (41pin)8200 pF (31pin)
0.022 µF (41pin)With no used (31pin)
fr = 1000 kHzfm = 1 kHz, 30%
Det
ecto
r ou
tput
— d
B
Frequency — Hz
Detector Output — Frequency Fig.42
Fig. 41
31 30+
–IF output Noise canceler input1 kΩ
1 µF2200 pF
A12089
H1 W12.5OU
–2.5OU–19.00 µs 981.00 µs
IF audio output f = 10 kHz,180 kHz dev
A12088Fig. 43
Fig. 44
4. Noise Canceler Block• The noise canceler input (pin 30) has an input impedance of about 50 kΩ. Check the low band frequency
characteristics carefully when determining the value of the coupling capacitor used. Note that fC will be about 3 Hzwhen a 1 µF capacitor is used in the application.
• Pins 8 and 9 are used to set the noise detector sensitivity and the noise AGC. It is advisable to first set the noisesensitivity for a medium field (an antenna input of about 50 dBµ) with pin 8 (the noise sensitivity setting pin), andthen set the AGC level for a weak field (20 to 30 dBµ) with pin 9 (the AGC adjustment pin). If the noise sensitivityis increased, the AGC will become more effective but, inversely, the weak field sensitivity will be reduced.
Noise canceler 10 kHz overmodulation malfunction may be a problem. In particular, when an overmodulatedsignal is input, the noise canceler may, in rare cases, malfunction. This is due to the fact that the IF detector outputhas a waveform of the type shown in figure 43 due to the bands of the IF ceramic filters as shown below. (Here, theantenna input is 60 dBµ, the ceramic filters are 150 kHz × 1 and 180 kHz × 2, f = 10 kHz, 180 kHz dev.) The noisecanceler reacts to the spikes (whiskers) generated due to this overmodulation, which results in distortion to theaudio output. (The spike components due to overmodulation occur due to the bands of the ceramic filters in thetuner.) The following describes a method for resolving this problem. This incorrect operation due toovermodulation is prevented by removing the spike components due to this overmodulation with a low-pass filterconsisting of a 1 kΩ resistor and a 2200 pF capacitor shown in figure 44. However, note that the FM separationcharacteristics in the high band and the AM frequency characteristics will change.
No. 6655-42/54
LA1787M
41
20 kΩ
C
To the matrix
A12090
VO(dB)
f(Hz)
2πC × 20 kΩ1
A12091
–60
–50
–40
–30
–20
–10
0
10
3 5 7 100 2 3 5 7 1k 2 3 5 7 10k 2 3
VCC = 8.0 Vf = 98 MHz 100%mod80 dBµ IN
Changes in the pin 41 capacitor capacitance (for a 100% high cut ratio)
0.0047 µF
0.0022 µF
0.001 µF
0.01 µF0 µF
Atte
nuat
ion,
HC
C —
dB
Frequency, f — Hz
Frequency Characteristics Fig.47
5. Multiplexer Block• HCC (high cut control) frequency characteristics (pin 41)
When the HCC function operates, the frequency characteristics of the output signal are determined by thecapacitance of the external capacitor connected to pin 41.
1fC = ——————— [Hz]
2π× C × 20 kΩ
Fig. 45
Fig. 46
17
30 –
1211
6800 pF 3.9 kΩ
18
0.01 µF 50 kΩ
Pilotcancel
Gate
To the multiplexer
Noise canceler input
A12092
• Pilot canceler adjustment (pins 17 and 18)
Fig. 48
The pilot canceler signal waveform (pin 19) is a 19 kHz signal that contains no third harmonic as shown in figure48. Since this signal has the same phase as the pilot signal, no capacitor is required between pin 18 and ground.Since it has no third harmonic component, excellent pilot cancellation can be acquired in both the left and rightchannels by adjusting with a variable resistor.
19
5 kΩ
0.047 µF C
To the subdecoder
A12093
20 kΩ
Larger
A12094
• Separation adjustment (pin 19)
The separation is adjusted by modifying the input level to the subdecoder with the variable resistor connected topin 19. Since only the sub-modulation level is changed by changing the variable resistor setting, the monaural(main) output level is not changed. Furthermore, degradation of high band separation in the decoder can be avoidedif the impedance of the external capacitor (C) in the subchannel frequency band (23 to 53 kHz) is made sufficientlysmaller than the variable resistor.
No. 6655-43/54
LA1787M
Fig. 49
++
24
S-meter
32 27
FMS-meter
MRC
6.4 kΩ10 kΩ
30 kΩ
3.6 kΩ 75 pF 1 kΩ
DC buffer
VCC
2 µA
100 Ω
QMRC
C27 VCC
To the SNC, pin 28
Noise amplifierHigh-pass filter with Fc = 70 kHz + amplifier
An external transistor equivalent to the 2SC536 is requiredReason: A QMRC level shifter is required to allow a simplified MRC circuit to be used in the LA1787M.
A11768
6. MRC Circuit
Fig. 50
No. 6655-44/54
LA1787M
+
32
A11769
(1) When there is no AC noise on pin 32V24 = V27–VBE
↑QMRC
V27 is about 2.5 V when the antenna input is 60 dB or higher.
(2) Since the MRC noise amplifier gain is fixed, the MRC circuit is adjusted by reducing the AC input level.
(3) The MRC attack and release are determined by C27 on pin 27.Attack: 7 µA · C27 → 2 µA · C27Release: 500 Ω · C27 → 100 Ω
Notes on the Noise CancelerThe noise canceler characteristics have been improved by implementing the circuit that determines the gate time inlogic. Since the time constant in earlier noise cancelers was determined by an RC circuit such as that shown in figure52, the rise time shown in figure 53 was influenced by the values of the resistor and capacitor used. As a result thenoise exclusion efficiency was reduced by this delay in the rise time. In the LA1787M, this rise time was shortened byimplementing the circuit that determines the gate time in logic, allowing it to reliably exclude noise.
Fig. 51
A11771 A11772
Fig. 52 Fig. 53
No. 6655-45/54
LA1787M
FM
RF
MIX IN 64 pin
1st IF IN 56 pin
2nd IF IN 51 pinANT IN
11 dB 12 dB 18 dB
A11773
Fig. 54
Gain Distribution (FM)This section investigates the gain in each block in the LA1787M when the Sanyo recommended circuits are used.
(Test conditions)Ambient temperature: 26°CAntenna and mixer input frequency: 98.1 MHzFirst and second IF input frequency: 10.7 MHz
The input levels when VSM = 2 V will be as follows.ANT IN: 19 dBµMIX IN: 30 dBµ1st IF IN: 42 dBµ2nd IF IN: 60 dBµ
When the gains for each block are determined according to the above, the results are as follows.RF GAIN: 11 dBMIX GAIN: 12 dB1st IF GAIN: 18 dB
No. 6655-46/54
LA1787M
(AM)This section investigates the gain in each block in the LA1787M when the Sanyo recommended circuits are used.
(Test conditions)Ambient temperature: 26°CAntenna and mixer input frequency: 1 MHzFirst and second mixer input frequency: 10.7 MHzSecond IF input frequency: 450 kHz
The gains at each stage will be as follows.RF Gain (ANT IN-pin62): 17 dB1st MIX Gain (pin62-pin56): 8 dB1st IF Gain (pin55-pin53): 15 dB
AM
RF
RFGain
1st MIXGain
1st IFGain
2nd MIXGain
2nd IFGain
A11774
1st MIX 1st IF 2nd MIX 2nd IF AM DET
Fig. 55
Input Circuits for Each Stage
[FM]• Mixer input • First IF input
No. 6655-47/54
LA1787M
A11775A11776
6250 Ω 0.022 µF
50 Ω
A11778
fr = RF
5250 Ω 0.022 µF
50 Ω
A11780
fr = 450 kHz
4550 Ω 0.022 µF
50 Ω
IFT
A11781
fr = 450 kHz
4950 Ω 0.022 µF
50 Ω
A11779
fr = 10.71 MHz (f2nd osc + 0.45 MHz)
A11777
63
64
75 Ω 0.022 µF
75 Ω
VIN
Actual measurement
5675 Ω 300 Ω 0.022 µF
75 Ω
fr = 10.7 MHz
51
50
75 Ω 300 Ω 0.022 µF
75 Ω 330 Ω
0.022 µF
fr = 10.7 MHz
• IF input
• IF input • Del input
[AM]• First mixer input • Second mixer input
Sample AM tuner Circuit with the LC72144 Used Together
No. 6655-48/54
LA1787M
RFCF CF CF
1st IF
2nd MIX
450K
300 Ω
IF
A11782
LC72144XBUFF
fosc
RFCF CF CF
1st MIX10.71 MHz
2nd OSC 1st OSC
IF
A11783
10.26 MHz
62
10 kΩ
AF
AFRF
CF CF Quadraturedetector
10.7 MHzIF
NC MPXRchLch
59 56 53 49 54 52
31
60
6364
60 56 53 5159
AM 1st IF Step FM IF
1 fOSC 10.25 MHz 10.7 MHz 10 kHz, 11 kHz 10.7 MHz
2 fOSC 10.35 MHz 10.8 MHz 9 kHz, 10 kHz 10.8 MHz
No. 6655-49/54
LA1787M
1 2 3
6 4
3
2
4
1 6
S
3
2
4
1 6
S
S S
3
2
4
1 6
S
[AM Block]AM FILTEER (SA-1051)
AM IF1 (SA-264)
AM OSC (SA-359)
AM IF2 (SA-1063)
3
2
4
1 6
S
3
2
4
1 6
S
AM loading (SA-1062)
0.1ø2UEW
AM RF amplifier (RC875-222J)
AM ANT IN (SA-1048)
3
2
4
1 6
S3
2
4
1 6
S
3
2
4
1 6
S
3
2
48
71 6
A136
S
SC1
C2
[FM Block]FM RF (SA-1060)
FM OSC (SA-1052)
FM ANT (SA-1061)
FM MIX (SA-266)
3
2
4
1 6
S S
FM DET (SA-208)
Crystal Oscillator ElementKinseki, Ltd.
Frequency: 10.26 MHzCL: 20 pFModel No.: HC-49/U-S
Coil SpecificationsSumida Electronics, Ltd.
No. 6655-50/54
LA1787M
1 2 3
6 4
3
2
4
1 6 0.1ø2UEW
3
2
4
1 6 0.05ø3UEW
3
2
4
1 6 0.05ø3UEW
[AM Block]
The Toko Electric Corporation
AM FILTEER (A2861BIS-15327)
AM IF1 (7PSGTC-5001A)
AM OSC (V666SNS-214BY)
AM IF2 (7PSGTC-5002Y)
3
2
4
1 6 0.05ø3UEW
3
2
4
1 6
S
S
AM loading (269ANS-0720Z)
0.1ø2UEW
AM RF amplifier (187LY-222)
AM ANT IN (385BNS-027Z)
3
2
4
1 6 S
S
ø0.1–2UEW
3
2
4
1 6 Sø0.1–2UEW
3
2
4
1 6 Sø0.12–2UEW
3
2 5
4
1 6 S
S
ø0.07–2UEW
[FM Block]FM RF (V666SNS-208AQ)
FM OSC (V666SNS-205APZ)
FM ANT (V666SNS-209BS)
FM MIX (371DH-1108FYH)
3
2
4
1 6 0.07ø2MUEW
FM DET (DM600DEAS-8407GLF)
No. 6655-51/54
LA1787M
1 2 3
6 4
3
2
4
1 6
S
5.1µH
3
2
4
1 6S S
180pF
3
2
4
1 6
S
180pF
[AM Block]
Sagami Elec Co., Ltd.
AM FILTEER (000021055)
AM IF1 (000021057)
AM OSC (000021056)
AM IF2 (000021059)
3
2
4
1 6
S
30mH
3
2
4
1 6
S
100µH
AM loading (000021061)
2.2mH
AM RF amplifier (000021063)
AM ANT IN (000021062)
3
2
4
1 6
S
S3
2
4
1 6
S
105.5nH
3
2
4
1 6
S
62.7nH
3
2 5
4
1 6
1-2 : 100pF2-3 : 100pF
S
S
[FM Block]FM RF (000021064)
FM OSC (000021066)
FM ANT (000021065)
FM MIX (000021067)
3
2
4
1 6
1-3 : 20µH3-4 : 120pF
SS
FM DET (010021075)
Coil Specifications
No. 6655-52/54
LA1787M
Out
put,
nois
e, A
M o
utpu
t, LR
out
put —
dB
HC
C, S
NC
, RF
AG
C, m
utin
g vo
ltage
,S
-met
er v
olta
ge, V S
M—
V
Antenna input — dBµ Antenna input — dBµ
Tot
al h
arm
onic
dis
tort
ion,
TH
D —
%
Antenna input — dBµ Antenna input — dBµ
Out
put,
nois
e —
dB
Out
put,
nois
e, A
M o
utpu
t — d
B
DC
V —
V
Mix
er o
utpu
t — d
Bµ
Input — dBµ Input — dBµ
Mixer input — dBµ
Firs
t IF
out
put —
dBµ
First IF input — dBµ
No. 6655-53/54
LA1787M
–100
–80
–60
–40
–20
0
20
–20 0 20 40 60 80 100 120 140
VCC = 8.5 Vf = 1 MHzmod = 1 k 30%
NOISE
OUT
ANT input, IN — dBµ
AM I/O Characteristics
Out
put,
nois
e —
dB
0
1.0
2.0
3.0
4.0
5.0
7.0
6.0
–20 0 20 40 60 80 100 120 140
VCC = 8.5 Vf = 1 MHz
RF AGC
IF AGC
VSM
ANT input, IN — dBµ
AM DC Characteristics
AG
C, S
-met
er v
olta
ge —
V
0
1.0
2.0
3.0
4.0
5.0
7.0
6.0
–20 0 20 40 60 80 100 120 140
VCC = 8.5 Vf = 1 MHzmod = 1 k 30% 80%
fm =
1 k
Hz
80%
fm =
1 k
Hz
30%
ANT input, IN — dBµ
AM Distortion
Tot
al h
arm
onic
dis
tort
ion,
TH
D —
%
Firs
t IF
out
put —
dB
Frequency, — MHz
Firs
t IF
out
put —
dB
Ant
enna
inpu
t — d
Bµ
S/N
, AM
out
put —
dB
AG
C o
n, s
epar
atio
n, in
put l
evel
— d
Bµ
Frequency, — MHz
Ambient temperature, Ta — °CAmbient temperature, Ta — °C
Sep
arat
ion,
Sep
— d
B
Ambient temperature, Ta — °C
LA1787M
PS No.6655-54/54
ON Semiconductor and the ON logo are registered trademarks of Semiconductor Components Industries, LLC (SCILLC). SCILLC owns the rights to a numberof patents, trademarks, copyrights, trade secrets, and other intellectual property. A listing of SCILLC’s product/patent coverage may be accessed atwww.onsemi.com/site/pdf/Patent-Marking.pdf. SCILLC reserves the right to make changes without further notice to any products herein. SCILLC makes nowarranty, representation or guarantee regarding the suitability of its products for any particular purpose, nor does SCILLC assume any liability arising out of theapplication or use of any product or circuit, and specifically disclaims any and all liability, including without limitation special, consequential or incidentaldamages. “Typical” parameters which may be provided in SCILLC data sheets and/or specifications can and do vary in different applications and actualperformance may vary over time. All operating parameters, including “Typicals” must be validated for each customer application by customer’s technicalexperts. SCILLC does not convey any license under its patent rights nor the rights of others. SCILLC products are not designed, intended, or authorized for useas components in systems intended for surgical implant into the body, or other applications intended to support or sustain life, or for any other application inwhich the failure of the SCILLC product could create a situation where personal injury or death may occur. Should Buyer purchase or use SCILLC products forany such unintended or unauthorized application, Buyer shall indemnify and hold SCILLC and its officers, employees, subsidiaries, affiliates, and distributorsharmless against all claims, costs, damages, and expenses, and reasonable attorney fees arising out of, directly or indirectly, any claim of personal injury ordeath associated with such unintended or unauthorized use, even if such claim alleges that SCILLC was negligent regarding the design or manufacture of thepart. SCILLC is an Equal Opportunity/Affirmative Action Employer. This literature is subject to all applicable copyright laws and is not for resale in any manner.
–80
–60
–40
–20
0
20
40 60 80 100 120 140
desire mod ON
Δ40 kHz
100 dBμ
80 dBμ60 dBμ40 dBμ
100 dBμ80 dBμ
60 dBμ
40 dBμdesiremodOFF
ANT input, IN — dBμ
AM Second-Channel Interference Rejection Characteristics
Out
put,
nois
e —
dB
50Ω
50Ω 50/3Ω
50/3Ω50/3Ω
30ΩVIN
15pF ANT IN
65pF
JIS ANT. DUMMYfu=1040kHzfm=400Hz 30%
fD=1MHzfm=1kHz 30%
–80
–60
–40
–20
0
20
40 60 80 100 120 140
desire mod ON
Δ400kHz
100 dBμ
80 dBμ60 dBμ40 dBμ
100
dBμ
80 d
Bμ
60 dBμ
40 dBμ
ANT input, IN — dBμ
Out
put,
nois
e —
dB
desiremodOFF
50Ω
50Ω 50/3Ω
50/3Ω50/3Ω
30ΩVIN
15pF ANT IN
65pF
JIS ANT. DUMMYfu = 1400 kHzfm = 400 Hz 30%
fD = 1 MHzfm = 1 kHz 30%
AM Second-Channel Interference Rejection Characteristics