LM1818.PDF

April 1987

LM1818 Electronically Switched Audio Tape System

General Description

The LM1818 is a linear integrated circuit containing all of the

active electronics necessary for building a tape recorder

deck (excluding the bias oscillator). The electronic functions

on the chip include: a microphone and playback preamplifi-

er, record and playback amplifiers, a meter driving circuit,

and an automatic input level control circuit. The IC features

complete internal electronic switching between the record

and playback modes of operation. The multipole switch

used in previous systems to switch between record and

playback modes is replaced by a single pole switch, thereby

allowing for more flexibility and reliability in the recorder de-

sign.*

*Monaural operation, Figure9.

Features

Y Electronic record/play switching

Y 85 dB power supply rejection

Y Motional peak level meter circuitry

Y Low noise preamplifier circuitry

Y 3.5V to 18V supply operation

Y Provision for external low noise input transistor

Typical Applications

TL/H/7894±1

FIGURE 1. Stereo Application Circuit (Left Channel Shown), V S e 15V

Order Number LM1818N

See NS Package Number N20A

C 1995 National Semiconductor Corporation

TL/H/7894

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.

Supply Voltage

Operating Temperature

0 § Cto a 70 § C

Junction Temperature

150 § C

18V

Minimum Voltage on Any Pin

b 0.1 V DC

Maximum Voltage on Pins 2 and 5

0.1 V DC

Package Dissipation, (Note 1)

1560 mW

Maximum Current Out of Pin 14

5 mA DC

Storage Temperature

b 65 § Cto a 150 § C

Lead Temperature (Soldering, 10 sec.)

260 § C

Electrical Characteristics V CC e 6V, T A e 25 § C, See Test Circuits (Figures2and3)

Parameter

Conditions

Min Typ Max Units

Operating Supply Voltage Range

3.5

V DC

Supply Current

Test Circuit (Figure2)

Turn-ON Time

Externally Programmable

400

Playback Signal to Noise

DIN Eq. (3180 and 120 m s), 20±20 kHz,

R S e 0, Unweighted, V REF e 1mV

at 400 Hz

Record Signal to Noise

Flat Gain, 20±20 kHz, R S e 0,

ALC OFF, V REF e 1mV

at 1 kHz, Unweighted

Fast Turn-ON Charging Current

Pins 16 and 17

200

m A

Record and Playback Preamplifier

f e 100 Hz

100

Open Loop Voltage Gain

Preamplifier Input Impedance

Pin 16 or Pin 17

k X

Preamplifier Input Referred PSRR

1 kHz Ð Flat Gain

Bias Voltage on Pin 18 in Play Mode

0.5

or Pin 15 in Record Mode

Monitor Amplifier Input

Pins 11 and 12

0.5

m A

Bias Current

Monitor Amplifier Open

Record or Playback, f e 100 Hz

Loop Voltage Gain

Monitor Output Current Capability

Pins 9 and 10, Source Current Available

400

750

m A

Monitor Amplifier Output Swing

R L e 10k, AC Load

1.2

1.65

Vrms

THD, All Amplifiers

At 1 kHz, 40 dB Closed Loop Gain

0.05

Record-Playback Switching Time

As in Test Circuit

Input ALC Range

D V IN for D V OUT e 8dB

Input Voltage on ALC Pin for

mVrms

Start of ALC Action

ALC Input Impedance 2 k X

ALC Attack Time C13 e 10 m F 7 ms

ALC Decay Time R17 e % , C13 e 10 m F 30 sec

Meter Output Gain 100 mVrms at 1 kHz into Pin 4 800 mV DC

Meter Output Current Capability 2 mA DC

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

of 80 § C/W junction to ambient.

TL/H/7894±2

FIGURE 2. General Test Circuit

Test Circuits (Continued)

TL/H/7894±3

FIGURE 3. Noise Test Circuit

Equivalent Schematic Diagram

TL/H/7894±4

FIGURE 4

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