Single 5-V Supply
High-Input-Impedance, High-Threshold
Receivers
Common Driver Strobe
TTL-Compatible Driver and Strobe Inputs
With Clamp Diodes
High-Speed Operation
100-mA Open-Collector Driver Outputs
Four Independent Channels
TTL-Compatible Receiver Output

description
The SN55138 and SN75138 quadruple bus
transceivers are designed for two-way data
communication over single-ended transmission
lines. Each of the four identical channels consists
of a driver with TTL inputs and a receiver with a
TTL output. The driver open-collector output is
designed to handle loads up to 100-mA open
collector. The receiver input is internally
connected to the driver output, and has a high
impedance to minimize loading of the
transmission line. Because of the high driveroutput
current and the high receiver-input
impedance, a very large number (typically
hundreds) of transceivers may be connected to a
single data bus.
The receiver design also features a threshold of 2.3 V (typical), providing a wider noise margin than would be
possible with a receiver having the usual TTL threshold. A strobe turns off all drivers (high impedance) but does
not affect receiver operation. These circuits are designed for operation from a single 5-V supply and include a
provision to minimize loading of the data bus when the power-supply voltage is zero.
The SN55138 is characterized for operation over the full military temperature range of –55°C to 125°C. The
SN75138 is characterized for operation from 0°C to 70°C.