Data communication circuits page

Index

Circuit translates TTY current loop to RS-232C - provides signal translation between a passive current-loop (TTY) interface and a duplex RS-232C ports
Current Loop Converter - Two Channel Isolated Industrial Version, schematic in pdf format
IC adds full-duplex RS-485 operation - simple RS-485 repeater provides full-duplex communications with only tow ICs
RS-232 to RS-422 conversion cable schematic - cable which can be used to connect computer RS-232 to some VCRs with RS-422 interface, zippled file packet
RS-232 to RS-485 Isolated Converter - information on commercial product, datyasheet includes full circuit diagram
Two Channel, Port Powered RS-232 to RS-422 Converter - information on commercial product, datyasheet includes full circuit diagram

MAX1480 - optically isolated RS-485 IC from Maxim, datasheet in PDF format
RS-232C interface meets telecomminications safety specs - RS-232 isolation circuit
RS-232C circuit has galvanic isolation - you can obtain longer transmission distances with the RS-232C interface if you use galvanic isolation between the two linked terminals
RS-232 to RS-232 Port-Powered Optical Isolator - brochure with schematic in pdf format

Circuit converts between TTL and shifted ECL
Digital Interface Level Conversion Chips and Circuits
Interfacing between CML, PECL and LVDS requires level-shift components
Logic Family Voltage Translation - how to translate between TTL, 74xx, CMOS, ECL, PECL, Low Voltage TTL, LVTTL, etc.
Simple RS-232 receiver - simple one transistor RS-232 level to TTL level converter
TTL to RS-232 interfacing
Two transistors form bidirectional level translator - illustrates a translation from 5 to 3V, but it can accommodate almost any other voltage levels, provided the logic-low levels are equal (usually 0V), translation from 1 to 100V are possible although slow

Circuit adapts differential input to drive coax - uses an HFA1100 or HFA1105 to convert a balanced input signal to a single-ended output signal, uses positive feedback to characteristic-impedance matching while increasing the available output swing, as compared with using a simple series termination resistor
DC power wire also carries clock or data - high-side current-sense amplifier, IC1, offers a simple method of combining low-speed clocks or other signals with dc power in cables between subsystems
Emissions killers trap common-mode currents - unshielded twisted-pair cable that is transformer-coupled to a digital system can easily act as a radiating antenna because of common-mode currents induced by unwanted stray coupling from the digital portions of the system
Group-delay equalizer has gain more than 1
Line driver economically synthesizes impedance - line-driver circuit uses a second op amp to synthesize the output impedance rather than inserting a power-hungry resistor in series with the op amp's output
RLC circuits match transmission lines to loads - you can use simple RLC circuits to compensate for the mismatch of high impedance CMOS input and transmission line
Speedy Spice subcircuit models lossy line - useful for simulating line driver designs

Correlator works in presence of noise - clipped-signal correlator outperforms any resistor-capacitor clipped-signal correlator, and the circuit has no race paths
SP-L modulator uses single-speed bit clock - circuit for producing Manchester encoding modulation easily

Synchronizing controller detects baud rate - a simple and inexpensive implementation using an eight-pin 12C508 controller (Microchip Technology, Chandler, AZ) provides both bit-rate detection and a synchronous, appended-clock output from an asynchronous input-data stream