Texas Instruments 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 μs/50 μs 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 0°C to 70°C. The SN65LBC184 is characterized from −40°C to 85°C.