The PRL-444 is a four channel TTL/CMOS input, 50 Ω output TTL/CMOS Line Driver. It is intended for interfacing with signal sources, such as digital I/O cards, that cannot drive 50 Ω loads to valid TTL levels. Each input has a 10 kΩ pulled up to 2.5 V so that it can also be driven by open-collector devices. The 50 Ω back-terminated outputs of the PRL-444 can drive long lines with or without 50 Ω load terminations. With 50 Ω load terminations, however, all outputs can drive 100 ft of 50 Ω cables at clock rates greater than 60 MHz.
If the inputs are left open, all outputs will go Hi, because the inputs are pulled up to +2.5 V. All outputs can be set to the Lo state by either setting the polarity inverting switch to the down position or terminating all inputs to 2 kΩ or lower. The polarity-inverting switch enables easy generation of four static TTL Hi/Lo logic signals when the inputs are not driven.
The PRL-444 is housed in a 1.3 x 2.9 x 2.9-in. extruded aluminum enclosure and is supplied with a ±8.5 V/±1.4 A AC/DC Adapter. A maximum of four units can share a single AC/DC adapter using the PRL-730 voltage distribution module. If mounting is desired, a pair of the #35001420 mounting brackets can accommodate any two PRL modules of the same length. Please refer to the Accessories Section of the literature for more detail.
A block diagram showing the equivalent input and output circuits of the PRL-444 is shown in Fig. 1.