17.05.2015 Views

~ National ~ Semiconductor - Al Kossow's Bitsavers

~ National ~ Semiconductor - Al Kossow's Bitsavers

~ National ~ Semiconductor - Al Kossow's Bitsavers

SHOW MORE
SHOW LESS

You also want an ePaper? Increase the reach of your titles

YUMPU automatically turns print PDFs into web optimized ePapers that Google loves.

~<strong>National</strong><br />

~ <strong>Semiconductor</strong><br />

MM74HC942 300 Baud Modem<br />

General Description<br />

The MM74HC942 is a full duplex low speed modem. It provides<br />

a 300 baud bidirectional serial interface for data communication<br />

over telephone lines and other narrow bandwidth<br />

channels. It is Bell 103 compatible.<br />

The MM74HC942 utilizes advanced silicon-gate CMOS<br />

technology. Switched capacitor techniques are used to perform<br />

analog signal processing.<br />

MODULATOR SECTION<br />

The modulator contains a frequency synthesizer and a sine<br />

wave synthesizer. It produces a phase coherent frequency<br />

shift keyed (FSK) output.<br />

LINE DRIVER AND HYBRID SECTION<br />

The line driver and hybrid are designed to facilitate connection<br />

to a 600n phone line. They can perform two-to-fourwire<br />

conversion and drive the line at a maximum of 0 dBm.<br />

DEMODULATOR SECTION<br />

The demodulator incorporates anti-aliasing filters, a receive<br />

filter, limiter, discriminator, and carrier detect circuit. The<br />

nine pole receive filter provides 60 dB of transmitted tone<br />

rejection. The discriminator is fully balanced for stable<br />

operation.<br />

Features<br />

• Drives 600n at 0 dBm<br />

• <strong>Al</strong>l filters on chip<br />

• Transmit level adjustment compatible with universal<br />

service order code<br />

• TTL and CMOS compatible logic<br />

• <strong>Al</strong>l inputs protected against static damage<br />

• ± 5V supplies<br />

• Low power consumption<br />

• Full duplex answer or originate operation<br />

• Analog loopback for self test<br />

• Power down mode<br />

Applications<br />

• Built-in low speed modems<br />

• Remote data collection<br />

• Radio telemetry<br />

• Credit verification<br />

• Stand-alone modems<br />

• Point-of-sale terminals<br />

• Tone signalling systems<br />

• Remote process control<br />

Connection and Block Diagrams<br />

Dual-In-Line Package<br />

Vee DND Vaa XTALS<br />

XTALD<br />

DSI<br />

TLA<br />

ALB 19 C1ND<br />

co 18 EXI<br />

CDT 17 TXA<br />

TLA-i---1<br />

RXD 18 RXAI<br />

Vcc 15 RXA2<br />

CDA 14 SQT<br />

XTALD 13 oil.<br />

XTALS 12 Vee<br />

DSI-ll---.... -j....----,<br />

TIlA -+--.... -C~<br />

FTLC 10 11 TXD<br />

Top View<br />

TL/F/5348-1<br />

Order Number MM54HC942* or<br />

MM74HC942'<br />

'Please look into Section 8, Appendix D for<br />

availability of various package types.<br />

EXI-l-.:==:;:..-----<br />

RXA1-1----t<br />

CDA COT FTLC<br />

TL/F/5348-2<br />

5-3

Hooray! Your file is uploaded and ready to be published.

Saved successfully!

Ooh no, something went wrong!