74VHC943WM
器件资料摘要：
TL/F/11679
74VHC943
300
Baud
Modem
(5V
Supply)
PRELIMINARY
October 1995
74VHC943
300 Baud Modem (5V Supply)
General Description
The 74VHC943 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 74VHC943 utilizes advanced silicon-gate CMOS tech-
nology. Switched capacitor techniques are used to perform
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 600X phone line. They can perform two to four wire
conversion and drive the line at a maximum of b9 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.
Features
Y
5V supply
Y
Drives 600X at b9 dBm
Y
All filters on chip
Y
Transmit level adjustment compatible with universal
service order code
Y
TTL and CMOS compatible logic
Y
All inputs protected against static damage
Y
Low power consumption
Y
Full duplex answer or originate operation
Y
Analog loopback for self test
Y
Power down mode
Y
Direct Pin and function replacement for the 74HC943
Applications
Y
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 signaling systems
Y
Remote process control
Commercial Package Number Package Description
74VHC943WM M20B 20-Lead Molded JEDEC SOIC (0.300 Wide)
74VHC943N N20A 20-Lead Molded DIP
Note: Surface mount packages are also available on Tape and Reel. Specify by appending the suffix letter
‘‘X’’ to the ordering code.
Connection Diagram
Pin Assignments for
SOIC and PDIP
TL/F/11679–1
TRI-STATE is a registered trademark of National Semiconductor Corporation.
C
1995 National Semiconductor Corporation RRD-B30M125/Printed in U. S. A.
74VHC943
300
Baud
Modem
(5V
Supply)
PRELIMINARY
October 1995
74VHC943
300 Baud Modem (5V Supply)
General Description
The 74VHC943 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 74VHC943 utilizes advanced silicon-gate CMOS tech-
nology. Switched capacitor techniques are used to perform
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 600X phone line. They can perform two to four wire
conversion and drive the line at a maximum of b9 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.
Features
Y
5V supply
Y
Drives 600X at b9 dBm
Y
All filters on chip
Y
Transmit level adjustment compatible with universal
service order code
Y
TTL and CMOS compatible logic
Y
All inputs protected against static damage
Y
Low power consumption
Y
Full duplex answer or originate operation
Y
Analog loopback for self test
Y
Power down mode
Y
Direct Pin and function replacement for the 74HC943
Applications
Y
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 signaling systems
Y
Remote process control
Commercial Package Number Package Description
74VHC943WM M20B 20-Lead Molded JEDEC SOIC (0.300 Wide)
74VHC943N N20A 20-Lead Molded DIP
Note: Surface mount packages are also available on Tape and Reel. Specify by appending the suffix letter
‘‘X’’ to the ordering code.
Connection Diagram
Pin Assignments for
SOIC and PDIP
TL/F/11679–1
TRI-STATE is a registered trademark of National Semiconductor Corporation.
C
1995 National Semiconductor Corporation RRD-B30M125/Printed in U. S. A.