SANYO LA1787M Datasheet

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Any and all SANYO products described or contained herein do not have specifications that can handle applications that require extremely high levels of reliability, such as life-support systems, aircraft’s control systems, or other applications whose failure can be reasonably expected to result in serious physical and/or material damage. Consult with your SANYO representative nearest you before using any SANYO products described or contained herein in such applications.

SANYO assumes no responsibility for equipment failures that result from using products at values that exceed, even momentarily, rated values (such as maximum ratings, operating condition ranges, or other parameters) listed in products specifications of any and all SANYO products described or contained herein.

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

• Multiplex

• 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

3159A-QIP64E (14 × 14)

Monolithic Linear IC

Ordering number : ENN6655

72602RM (OT) No. 6655-1/54

SANYO Electric Co.,Ltd. Semiconductor Company

TOKYO OFFICE Tokyo Bldg., 1-10, 1 Chome, Ueno, Taito-ku, TOKYO, 110-8534 JAPAN

Single-Chip Tuner IC for Car Radios

LA1787M

14.0

17.2

14.0

17.2

0.15

0.35

0.8

(2.7)

3.0max

0.1

0.8

(1.0)

116

3348

Allowable power dissipation,

Pdmax — mW

Ambient temperature, Ta — °C

Mounted on a 40 × 80 × 1.3 mm

glass epoxy printed circuit board

Independent IC

SANYO: QIP64E (14 × 14)

[LA1787M]

Ratings

Parameter Symbol Conditions

min typ max

unit

[FM Characteristics] At the FM IF input Current drain I

CCO

-FM No input, I40 + I45 + I54 + I59 + I60 + I61 60 94 110 mA

Demodulation output V

-FM 10.7 MHz, 100dBµ, 1 kHz, 100%mod, The pin 15 output 205 310 415 mVrms

Pin 31 demodulation output V

-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, f

= 1 kHz, 30% AM, pin 15 55 68 dB

Att-1

10.7 MHz, 100 dBµ, 1 kHz. The pin 15 5 10 15 dB

attenuation when V33 goes from 0 to 2 V

Muting attenuation Att-2

10.7 MHz, 100 dBµ, 1 kHz. The pin 15

15 20 25 dB

attenuation when V33 goes from 0 to 2 V

Att-3

10.7 MHz, 100 dBµ, 1 kHz. The pin 15

28 33 38 dB

attenuation when V33 goes from 0 to 2 V

Separation Separation

10.7 MHz, 100 dBµ, L+R = 90%, pilot = 10%. The pin 15 output

30 40 dB

ratio 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 AttSNC

10.7 MHz, 100 dBµ, L-R = 90%, pilot = 10%.

1 5 9 dB

V28 = 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 attenuation

V29 = 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 such

33 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 V

IFBUFF-FM

10.7 MHz, 100 dBµ, unmodulated. The pin 23 output 130 200 270 mVrms

FM-1 No input. The pin 24 DC output, unmodulated 0.0 0.1 0.3 V

Signal meter output

FM-2 50 dBµ. The pin 24 DC output, unmodulated 0.4 1.0 1.5 V

FM-3 70 dBµ. The pin 24 DC output, unmodulated 2.0 2.7 3.5 V

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 V

MUTE-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

Continued on next page.

No. 6655-2/54

LA1787M

Specifications

Maximum Ratings at Ta = 25°C

Operating Conditions at Ta = 25°C

Parameter Symbol Conditions Ratings Unit

Maximum supply voltage

1 max Pins 6, 40, and 61 9 V

2 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 voltage

Pins 6, 7, 40, 45, 54, 59, 60, and 61 8 V

ST IND Pin 26 5 V

Operating supply voltage range V

op 7.5 to 9.0 V

Ratings

Parameter Symbol Conditions

min typ max

unit

[FM FE Mixer Input N-AGC on input V

-AGC

83 MHz, unmodulated.

81 88 95 dBµ

The input such that the pin 2 voltage is 2.0 V or below

W-AGC on input VWAGC

83 MHz, unmodulated. The input such that the pin 2

104 110 116 dBµ

voltage 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 V

OSCBUFFFM

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 SN

The level of a 1 = kHz, 1-µs pulse input that starts

40 mVp-o

noise canceller operation. Measured at pin 30.

The pulse rejection effect provided by the noise canceller. NC effect SN-NC

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) [Multipath Rejection Circuit] MRC input (pin 27) MRC output VMRC V24 = 5 V 2.2 2.3 2.4 V

MRC operating level MRC-ON

The pin 32 input level at f = 70 kHz such that

10 15 20 mVrms

pin 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, f

= 1 kHz, 30% modulation, pin 15 20 dB

Detector output V

-AM 1 MHz, 74 dBµ, fm= 1 kHz, 30% modulation, pin 15 130 195 270 mVrms

Pin 31 detector output V

-AM31 1 MHz, 74 dBµ, fm= 1 kHz, 30% modulation, pin 31 110 175 230 mVms

AGC F.O.M. V

AGC-FOM

1 MHz, 74 dBµ, referenced to the output, the input amplitude

51 56 61 dB

such 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, f

= 1 kHz, 80% modulation 0.3 1 %

Signal meter output

AM-1 No input 0.0 0.2 0.5 V

AM-2 1 MHz, 130 dBµ, unmodulated 4.8 6 7.3 V

Oscillator buffer output V

OSCBUFF AM1

No input, the pin 15 output 185 230 mVrms

Wide band AGC sensitivity

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 sensitivity

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 dBµ

IF buffer output V

IFBUFF-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.

Continued from preceding page.

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

• 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.

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

8 V

1 5 V SD, stereo, seek/stop

2 0.1 V / 0.7 V / 2 V / 4 V

These levels

Keyed AGC, Mute ATT

3 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 V

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

Pin Descriptions

No. 6655-6/54

LA1787M

ANT

1000pF

100Ω

300Ω

62 pin

RF AGC

A13555

AGC

DET

W AGC DET

KEYED

AGC

ANT

DAMPING DRIVER

12kΩ

FET

2nd GATE

A13556

25pF

20pF

2kΩ

A13557

An antenna damping current flows

1 Antenna damping drive when the RF AGC voltage (pin 2)

reaches V

– VD.

2 RF AGC

Used to control the FET second gate.

4 OSC Oscillator connection

AM first oscillator

7 AM OSC

This circuit can oscillator up to the SW band. An ALC circuit is included.

Continued on next page.

A L C

A13558

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, GND

Ground for the N.C., MPX, and MRC circuits.

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)

Memory circuit connection

Recording circuit used during

12 noise canceller operation.

Continued from preceding page.

Continued on next page.

3kΩ

15kΩ

200Ω

8 9

3kΩ

1MΩ

Differential

amp

0.01µF

0.01µF 6800pF

13 12 11

3.9kΩ

0.47µF

A13559

circuit

Gate

LPF

N.C

12 13

0.01µF

30kΩ

A13560

PLL

A13561

No. 6655-8/54

LA1787M

Pin No. Function Description Equivalent circuit

15 MPX output (left)

Deemphasis

16 MPX output (right)

50 µs: 0.015 µF

75 µs: 0.022 µF

Adjustment is required since the

pilot signal level varies with the

17 Pilot canceller signal output sample-to-sample variations in

the IF output level and other

parameters.

18 Pilot canceller signal output

Pin 18 is the output pin for the

pilot canceller signal.

Continued from preceding page.

Continued on next page.

3.3kΩ

0.015µF 0.015µF

20kΩ

10kΩ

17 18

0.01µF

100kΩ

A13562

6.7kΩ

A13563

17 18

0.01µF

100kΩ

1.5kΩ

A13564

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.)

Use a trimmer to adjust the

Separation subdecoder input level. adjustment pin (The output level is not modified in

mono and main modes.)

21 PHASE COMP. 22 PHASE COMP.

Continued from preceding page.

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Composite signal

4kΩ

REF

5kΩ

CSB 912 JF108

10pF

DECODER

30kΩ

0.047µF

A13565

A13566

REF

15kΩ

19kΩ

15kΩ

21 22

A13567

No. 6655-10/54

LA1787M

Pin No. Function Description Equivalent circuit

Continued from preceding page.

Continued on next page.

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.

IF counter buffer seek/stop During FM reception: switching 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

24 AM/FM signal meter Fixed-current drive signal meter

output

In AM mode, pin 32 outputs a

32 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 pin

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.

4.9V

S-meter

AM/FM

1.3V

50F

–

Forced SD: 2.5V

AM MUTE

IF counter

buffer

SEEK 5V

A13568

+ –

50kΩ

10kΩ

150Ω

51kΩ

STOP

BUFF.

10kΩ

Outputs a 1-mA current during AM reception

MRC

AM/FMSDStereo

Seek/stop

switching

100kΩ

AM/FM

indicator

A13570

A13569

No. 6655-11/54

LA1787M

Pin No. Function Description Equivalent circuit

Continued from preceding page.

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The MRC detector time constant

27 MRC control voltage time

is determined by a 100 Ω resistor

constant

and C2 when discharging and by the 2-µA current and C2 when charging.

28 SNC control input

The sub-output is controlled by a 0 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 kΩ when controlling with the pin 32 FM S-meter signal.

2µA

REF

100Ω

Pin 28

A13571

A13572

REF

1µF

A13573

No. 6655-12/54

LA1787M

Pin No. Function Description Equivalent circuit

Continued from preceding page.

Continued on next page.

30 Noise canceller input

Pin 30 is the noise canceller input. The input impedance is 50 kΩ.

Pin 31 is the AM and FM detector output In FM mode, this is a lowimpedance output.

31 AM/FM detector output In AM mode, the output

impedance is 10 kΩ. To improve the low band separation, use a coupling capacitor of over 10 µF.

FM S-meter output block

32 IF S-meter output and MRC

MRC AC input block

DC input

Adjust the external 1-kΩ resistor to attenuate the MRC AC input and control the circuit.

•The muting time constant is

determined by an external RC circuit as described below. Attack time: T

= 10 kΩ × C1

Release time: T

= 50 kΩ × C1

•Noise convergence adjustment

33 Mute drive output 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.

FM detector output

detector

10kΩ

1µF

Noise canceller

50kΩ

4.2V

A13574

1µF

1kΩ

MRC input

SEEK OFF

SOFT

MUTE

HOLE

DET

Band

muting

0.1µF

A13575

50kΩ

10kΩ

50kΩ

MUTE AMP.

SD circuit

A13576

No. 6655-13/54

LA1787M

Pin No. Function Description Equivalent circuit

Continued from preceding page.

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•The resistor R

determines the width of the band muting function. Increasing the value of R

narrows the band. Reducing the value of R

widens

the band.

34 AGC 35 QD output

•Null voltage

36 QD input

When tuned, the voltage between

37 V

REF

pins 34 and 37, V

34 – 37

, will be 0 V. The band muting function turns on when |V

34 – 37

| ≥ 0.7 V.

= 4.9 V

A 130-µA current flows from pin

38 FM SD ADJ

38 and, in conjunction with the external resistance R, determines the comparison voltage.

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

39 Keyed AGC becomes lower than the voltage

AM stereo buffer determined by the resistor

between pin 39 and ground.

This pin also is used as the AM stereo IF buffer pin.

0.1µF

REF

37 36 35 34

HOLE

DET

IF limitter amplifier

Quadrature

detector

3pF

SD ADJ

390Ω

1kΩ

Band

muting

A13577

130µA

KEYED

AGC

AM IF out

S-meter

Comparator

+ –

1.3V

50pF

150Ω

–

S-meter

A13578

6.4kΩ

3.6kΩ

90µA

A13579

No. 6655-14/54

LA1787M

Pin No. Function Description Equivalent circuit

Continued from preceding page.

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The HCC frequency characteristics

41 HCC capacitor

are determined by the external capacitor connected at this pin.

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.

Note: The LC capacitor must be

connected between this pin and V

(pin 40).

42 AM L.C. pin This is because the detector

circuit operates referenced to V

The cutoff frequency f

is determined by the following formula.

= 1/2π × 50 kΩ × C

Inserting a 1-MΩ resistor between

43 Pilot detector pin 43 and V

will force the IC

to mono mode.

20kΩ

DET

2200pF

A13580

50kΩ

1kΩ

+ –

1kΩ

A13581

19kHz∠0°

BIAS

30kΩ

1µF

A13582

No. 6655-15/54

LA1787M

Pin No. Function Description Equivalent circuit

45 IF output The IF amplifier load

Continued from preceding page.

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G1; Used for time constant switching during seeks.

• Reception τ = 2.2 µF × 300 kΩ

44 IF AGC

• Seek

τ = 2.2 µF × 10 Ω The external capacitors are connected to V

. This is because the IF amplifier operates referenced to V

AM antenna damping I46 = 6 mA (maximum)

46 drive output This is the antenna damping

Wide band AGC input current.

DET

SEEK

0.022µF

10Ω

240kΩ

50kΩ

Pin 40 V

2.2µF

IF AGC

A13583

Pin 40 V

DET

A13584

50pF

100Ω

ANT DAMPING DRIVER

20kΩ

W.AGC AMP.

A13585

No. 6655-16/54

LA1787M

Pin No. Function Description Equivalent circuit

52 IF input The input impedance is 2 kΩ.

Continued from preceding page.

Continued on next page.

FM muting on level

Modify the value of the external

adjustment

resistor to adjust the muting on level.

RF AGC rectification capacitor The low frequency distortion is determined as follows: Increasing C48 and C57 improves

48 RF AGC bypass the distortion but makes the 57 RF AGC response slower.

Reducing C48 and C57 aggravates the distortion but makes the response faster.

50 IF bypass 51 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.

30kΩ

140µA

Pin 24

– +

Inverter

MUTE

A13586

3.3µF

For AGC use

47µF

0.022µF

IF in

5.6V

2.6V

330Ω

10kΩ

Antenna

damping

–

A13587

10kΩ

A13588

2kΩ

100Ω

A13589

No. 6655-17/54

LA1787M

Pin No. Function Description Equivalent circuit

Continued from preceding page.

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• Input and output pin or the first

IF amplifier

• Inverting amplifier

53 IF amplifier output V56 = 2 V 56 IF amplifier input Input impedance: R

= 330 Ω

V53 = 5.3 V Output impedance R

OUT

= 330 Ω

The mixer coil connected to the

54 Mixer output: 130 µA

pin 54 mixer output must be

49 Mixer input

wired to V

(pin 40).

The pin 49 mixer input impedance is 330 Ω

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 W-AGC IN Pin 55 functions as the SD

AM 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 by comparing V55 with the S-meter voltage.

IF OUT

IF IN

Pin 40 V

300Ω

2.75V

Pin 40 VCC

300Ω

A13590

MIX IN

MIX

OUT

OSC

330Ω

A13591

62 pin

30pF

W-AGC N-AGC

50pF

50µA

+ –

AM SD

Signal meter

A13592

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