LM3661AM [NSC]

LM3361A Low Voltage/Power Narrow Band FM IF System; LM3361A低电压/功率窄带调频中频系统


型号：	LM3661AM
厂家：	National Semiconductor
描述：	LM3361A Low Voltage/Power Narrow Band FM IF System LM3361A低电压/功率窄带调频中频系统
文件：	总6页 (文件大小：156K)
中文：	中文翻译
下载：	下载PDF数据表文档文件

August 1989

LM3361A Low Voltage/Power Narrow Band FM IF System

General Description

Features

Functions at low supply voltage (less than 2V)

The LM3361A contains a complete narrow band FM de-

modulation system operable to less than 2V supply voltage.

Blocks within the device include an oscillator, mixer, FM IF

limiting amplifier, FM demodulator, op amp, scan control,

and mute switch. The LM3361A is similar to the MC3361

with the following improvements: the LM3361A has higher

voltage swing both at the op amp and audio outputs. It also

has lower nominal drain current and a squelch circuit that

draws significantly less current than the MC3361. Device

pinout functions are identical with some slightly different op-

erating characteristics.

Highly sensitive ( 3 dB limiting at 2.0 mV input typical)

High audio output (increased 6 dB over MC3361)

Low drain current (2.8 mA typ., V

3.6V)

Minimal drain current increase when squelched

Low external parts count

Block Diagram and Test Circuit

TL/H/5586–1

Order Number LM3661AM

or LM3361AN

T1-TOKO RMC-2A6597HM

CF-MURATA CFU 455E

See NS Package Number

M16A or N16E

1995 National Semiconductor Corporation

TL/H/5586

RRD-B30M115/Printed in U. S. A.

Absolute Maximum Ratings

If Military/Aerospace specified devices are required,

please contact the National Semiconductor Sales

Office/Distributors for availability and specifications.

Soldering Information

Dual-In-Line Package

Soldering (10 seconds)

260 C

Package Dissipation (Note 1)

Power Supply Voltage (V )

1500 mW

12 V

Small Outline Package

Vapor Phase (60 seconds)

Infrared (15 seconds)

215 C

220 C

RF Input Voltage (V 3.6V)

1 Vrms

See AN-450 ‘‘Surface Mounting Methods and Their Effect

on Product Reliability’’ for other methods of soldering sur-

face mount devices.

Mute Function (pin 14)

0.7 to 5 Vp

0 C to 70 C

55 C to 150 C

Operating Ambient Temperature Range

Storage Temperature Range

Parameters Guaranteed By Electrical Testing

1 kHz, 50X source)

MOD

(Test ckt., T

25 C, V

3.6V, f

10.7 MHz, Df

3 kHz, f

Parameter

Measure

Min

Typ

Max

Units

Supply Voltage Range

2.0

3.6

9.0

Supply Current

Squelch Off

Squelch On

2.8

3.6

5.0

6.0

RF Input for 3 dB Limiting

RF Input

2.0

350

1.5

6.0

Recovered Audio at Audio Output

Audio Out DC

Audio Output

200

1.2

RMS

1.8

Op Amp Gain

11 IN

Op Amp Output DC

0.4

0.7

Op Amp Input Bias Current

)/1MX

Scan Voltage

Pin 12 high (2V)

Pin 12 Low (0V)

0.5

3.0

3.4

Mute Switch Impedance, Pin 12

Switch S1 from pos.1 to pos.2

DV /DI

Design Parameters Not Tested or Guaranteed

Typ

Mixer Conversion Gain (Note 2)

Mixer Input Resistance

Mixer Input Capacitance

Detector Output Impedance

Squelch Hysterisis

3.6

V/V

2.2

500

100

Mute Off Impedance (measure pin 14 with pin 12 2V)

Squelch Threshold

0.65

0.15

V/kHz

Detector Center Frequency Slope

Note 1. For operation above 25 C ambient temperature, the device must be derated based on 150 C maximum junction temperature and a thermal resistance i

of 80 C/W.

Note 2. Mixer gain is supply dependent and effects overall sensitivity accordingly (See Typical Performance Characteristics).

Coils:

Filters:

Toko America

Murata

1250 Feehanville Drive

Mount Prospect, IL 60056

(312) 297-0070

2200 Lake Park Drive

Smyrna, GA 30080

(404) 436-1300

Typical Performance Characteristics (Test Circuits)

TL/H/5586–2

Internal Schematic

Applications Information (See Internal Schematic)

OSCILLATOR

tic, also increases distortion (see Typical Performance

Characteristics). For proper operation, the voltage swing on

pin 8 should be adequate to drive the upper rank of the

multiplier into switching (about 100 mVrms). This voltage

level is dependent on the internal 10 pF capacitor and the

The Colpitts type oscillator is internally biased with a regu-

lated current source which assures proper operation over a

wide supply range. The collector, base, and emitter termi-

nals are at pins 4, 1, and 2 respectively. The crystal, which

is used in the parallel resonant mode, may be replaced with

an appropriate inductor if the application does not require

the stability of a crystal oscillator. In this case, the resonant

frequency will be determined by the inductor in parallel with

the series combination of C1 and C2.

tank R voltage divider network. After detection and de-em-

phasis, the audio output at pin 9 is buffered by an emitter

follower.

OP AMP

The op amp inverting input (pin 10) which is internally refer-

enced to 0.7V, receives dc bias from the output at pin 11

through the external feedback network. Because of the low

D.C. bias, maximum swing on the op amp output with 10%

distortion is 500 mVrms. This can be increased when oper-

ating on supplies over 2.3V by adding a resistor from the op

amp input to ground which raises the quiescent D.C. at the

output allowing more swing (see figure below for selection

of added resistor). The op amp is normally utilized as either

a bandpass filter to extract a specific frequency from the

audio output, such as a ring or dial tone, or as a high pass

filter to detect noise due to no input at the mixer. The latter

condition will generate a signal at the op amp output, which

when applied to pin 12 can mute the external audio amp.

For max swing: V

)/2 (from internal circuit)

OUT

TL/H/5586–4

so Ct (C1)(C2)/(C1 C2)

)/2 0.7

so (V

and f

.159/ L(Ct)

MIXER

therefore

1.4

The mixer is double balanced to reduce spurious responses.

The upper pairs are switched by the oscillator while the RF

input is applied to the lower pair (pin 16). R43 sets the mixer

input impedance at 3.6 kX. The mixer output impedance of

1.8 kX will properly match the input impedance of a ceramic

filter which is used as a bandpass filter coupling the mixer

output to the IF limiting amplifier.

IF LIMITER

TL/H/5586–5

The IF amplifier consists of six differential gain stages, with

the input impedance set by R2 at 1.8 kX to properly termi-

nate the ceramic filter driving the IF. The IF alone (without

Increasing OP Amp Swing

SQUELCH TRIGGER CIRCUIT

mixer) has a 3 dB limiting sensitivity of approximately 50

The squelch trigger circuit is configured such that a low bias

on the input (pin 12) will force pin 13 high (200 mV below

supply), where it can support at least a 1 mA load, and pin

14 to be a low impedance, typically 15X to ground. Con-

necting pin 14 to a high impedance ground reference point

in the audio path between pin 9 and the audio amp will mute

the audio output. Pulling pin 12 above mute threshold

(0.65V) will force pin 13 to an impedance of about 60 kX to

ground and pin 14 will be an open circuit. There is 100 mV

of hysterisis at pin 12 which effectively prevents jitter.

mV. The system bandwidth is limited to about 5 MHz due to

high impedances in the IF which are necessary to meet low

power requirements. The IF output is connected to the ex-

ternal quad coil at pin 8 via an internal 10 pF capacitor.

FM DEMOD AUDIO OUT

A conventional quadrature detector is used to demodulate

the FM signal. The Q of the quad coil, which is determined

by the external resistor placed across it, has multiple effects

on the audio output. Increasing the Q increases output level

but because of nonlinearities in the tank phase characteris-

Physical Dimensions inches (millimeters)

Molded Small Outline Package (M)

Order Number LM3361AM

NS Package Number M16A

Molded Dual-In-Line Package (N)

Order Number LM3361AN

NS Package Number N16E

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DEVICES OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT OF NATIONAL

SEMICONDUCTOR CORPORATION. As used herein:

1. Life support devices or systems are devices or

systems which, (a) are intended for surgical implant

into the body, or (b) support or sustain life, and whose

failure to perform, when properly used in accordance

with instructions for use provided in the labeling, can

be reasonably expected to result in a significant injury

to the user.

2. A critical component is any component of a life

support device or system whose failure to perform can

be reasonably expected to cause the failure of the life

support device or system, or to affect its safety or

effectiveness.

National Semiconductor

Corporation

National Semiconductor

Europe

National Semiconductor

Hong Kong Ltd.

National Semiconductor

Japan Ltd.

1111 West Bardin Road

Arlington, TX 76017

Tel: 1(800) 272-9959

Fax: 1(800) 737-7018

Fax:

(

49) 0-180-530 85 86

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LM3661AM [NSC]

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