MM74HC942N National Semiconductor, MM74HC942N Datasheet

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MM74HC942N

Manufacturer Part Number
MM74HC942N
Description
MM74HC942N_National.pdf
Manufacturer
National Semiconductor
Datasheet

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C 1995 National Semiconductor Corporation
MM74HC942 300 Baud Modem
General Description
The MM74HC942 is a full duplex low speed modem It pro-
vides a 300 baud bidirectional serial interface for data com-
munication over telephone lines and other narrow band-
width channels It is Bell 103 compatible
The MM74HC942 utilizes advanced silicon-gate CMOS
technology Switched capacitor techniques are used to per-
form analog signal processing
MODULATOR SECTION
The modulator contains a frequency synthesizer and a sine
wave synthesizer It produces a phase coherent frequency
shift keyed (FSK) output
LINE DRIVER AND HYBRID SECTION
The line driver and hybrid are designed to facilitate connec-
tion to a 600
wire conversion and drive the line at a maximum of 0 dBm
DEMODULATOR SECTION
The demodulator incorporates anti-aliasing filters a receive
filter limiter discriminator and carrier detect circuit The
nine pole receive filter provides 60 dB of transmitted tone
rejection The discriminator is fully balanced for stable
operation
Connection and Block Diagrams
Order Number MM54HC942 or
Dual-In-Line Package
MM74HC942
Top View
phone line They can perform two-to-four-
TL F 5348–1
TL F 5348
Features
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Applications
Y
Y
Y
Y
Y
Y
Y
Y
TRI-STATE is a registered trademark of National Semiconductor Corp
Drives 600
All filters on chip
Transmit level adjustment compatible with universal
service order code
TTL and CMOS compatible logic
All inputs protected against static damage
Low power consumption
Full duplex answer or originate operation
Analog loopback for self test
Power down mode
Built-in low speed modems
Remote data collection
Radio telemetry
Credit verification
Stand-alone modems
Point-of-sale terminals
Tone signalling systems
Remote process control
g
5V supplies
at 0 dBm
RRD-B30M105 Printed in U S A
January 1988
TL F 5348 – 2

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MM74HC942N Summary of contents

Page 1

... Analog loopback for self test Y Power down mode Y Applications Built-in low speed modems Y Remote data collection Y Radio telemetry Y Credit verification Y Stand-alone modems Y Point-of-sale terminals Y Tone signalling systems Y Remote process control Y TRI-STATE is a registered trademark of National Semiconductor Corp RRD-B30M105 Printed January 1988 TL F 5348 – 2 ...

Page 2

... Absolute Maximum Ratings If Military Aerospace specified devices are required please contact the National Semiconductor Sales Office Distributors for availability and specifications Supply Voltage ( Supply Voltage ( Input Voltage ( Output Voltage ( OUT BB Clamp Diode Current ( Output Current per pin (I ) OUT GND Current per pin (I ...

Page 3

AC Electrical Characteristics Unless otherwise specified all specifications apply to the MM74HC942 over the range 10 10% and a 3 579MHz Symbol Parameter TRANSMITTER F Carrier Frequency Error CE Power Output 2nd ...

Page 4

Description of Pin Functions Pin Name Function No 1 DSI Driver Summing Input This may be used to transmit externally generated tones such as dual tone multifrequency (DTMF) dialing sig- nals 2 ALB Analog Loop Back A logic high on ...

Page 5

Functional Description (Continued) THE DEMODULATOR SECTION The Receive Filter The demodulator recovers the data from the received sig- nals The signal from the hybrid is a mixture of transmitted signal received signals and noise The first stage of the receive ...

Page 6

... Note The efficiency of the acoustic coupling will set the valves of R1 and R2 Power supply decoupling close to the device is recommend- ed Ground loops should be avoided For further discussion of these subjects see the Audio Radio Handbook published by National Semiconductor Corporation 5348– 5348– 5 ...

Page 7

7 ...

Page 8

... National does not assume any responsibility for use of any circuitry described no circuit patent licenses are implied and National reserves the right at any time without notice to change said circuitry and specifications Order Number MM74HC942J NS Package J20A Order Number MM74HC942N NS Package N20A 2 A critical component is any component of a life ...

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