Transient Voltage Suppression Differential Transceiver

The SN75LBC184 and SN65LBC184 are differential data line transceivers in the trade-standard footprint of the SN75176 with built-in protection against high-energy noise transients. This feature provides a substantial increase in reliability for better immunity to noise transients coupled to the data cable over most existing devices. Use of these circuits provides a reliable low-cost direct-coupled (with no isolation transformer) data line Interface without requiring any external components.
The SN75LBC184 and SN65LBC184 CAN withstand overvoltage transients of 400-W peak (typical). The conventional combination wave called out in IEC 61000-4-5 simulates the overvoltage transient and models a unidirectional surge caused by overvoltages from switching and secondary lightning transients.
A biexponential function defined by separate rise and fall times for voltage and current simulates the combination wave. The standard 1.2 s/50 s combination waveform is shown in Figure 1 and in the test description in Figure 15.
The device also includes additional desirable features for party-line data buses in electrically noisy environment applications including industrial process control. The differential-driver design incorporates slew-rate-controlled outputs sufficient to transmit data up to 250 kbps. Slew-rate control allows longer unterminated cable runs and longer stub lengths from the main backbone than possible with uncontrolled and faster voltage transitions. A unique receiver design provides a fail-safe output of a high level when the inputs are left floating (open circuit). The SN75LBC184 and SN65LBC184 receiver also includes a high input resistance equivalent to one-fourth unit load allowing connection of up to 128 similar devices on the bus.
The SN75LBC184 is characterized for operation from 0C to 70C. The SN65LBC184 is characterized from ?40C to 85C.
By Texas Instruments