4 Ch. RS-422 Receiver, TTL Outputs


$ 1,138.50


  • Differential RS-422 to TTL Logic Level Translation
  • Conversion of Differential Signals Transmitted through Long Lines to Single-Ended TTL Signals
  • Mini Modular Instrument for interfacing with High Speed Data Communications Equipment


  • 75 MHz Typical Maximum Clock Rate
  • Floating 124 Differential Inputs Accept RS-422 or source-biased LVPECL inputs
  • 4 Single-Ended 50 Ω Back-Terminated TTL Outputs deliver 2.5 V into 50 Ω or 5 V into Hi-Z, typical
  • SMA or RJ45 I/O Connectors
  • Single Supply operation, +7.5 VDC to +12 VDC
  • Ready-to-Use 1.3 x 2.9 x 2.9-in. Module includes a ±8.5 V/1.7 A AC/DC Adapter


The PRL-425QRT is a four channel, differential input receiver with single-ended 50 Ω TTL output line drivers. It is intended for converting differential signals transmitted through long lines into single-ended TTL outputs. The floating 124 Ω inputs are designed to be compatible with RS-422 input signals. They can also accept source-biased LVPECL inputs. The 50 Ω back-terminated TTL output line drivers can drive long lines with or without terminations, and they are designed specifically for use with high speed data communication applications. Fig. 1 shows the standard RS-422 input configuration. A functional block diagram of this device is shown in Fig. 2.

A feature of the RS422 receiver chip in the PRL-425QRT is a “fail safe” state that sets the output logic Hi (TTL True) if the inputs are at the same voltage, which occurs if the inputs are left to float open or if they are shorted to GND. If this is undesired in your application, please consider the PRL-425T, 2 Ch. Universal Differential Receiver with TTL Outputs.

Each PRL-425QRT is supplied with a 8.5 V/1.7 A AC/DC Adapter, but it can also operate from a single positive power supply in the range of 7.5 V to 12 V. The PRL-425QRT-SMA has SMA I/Os and is housed in a 1.3 x 2.9 x 2.9-in. extruded aluminum enclosure, while the PRL-425QRT-RJRJ has RJ45 I/Os and a length of 3.9-in.

The PRL-425QRT-RJRJ allows the replacement of up to 12 coax cables by 2 double-shielded Cat7/Cat8 network cables to reduce cabling and complexity in high-density applications. While Cat7/Cat8 cabling was designed to carry differential signaling, such as RS422, the shielded twisted pairs have a single-ended impedance of ~54 Ohms when one wire is grounded, and they can carry single-ended TTL signals at up to 100 MHz, as shown in our impedance study.

A future version, PRL-425QRT-RJS, with RJ45 inputs and SMA outputs, is planned, but with no guarantee of an availability date.

Available accessories include TTL Fanout modules, voltage distribution modules, brackets for mounting multiple units, and a rackmount enclosure kit for rapid system integration.

Fig 1., RS422 Input Configuration
Fig 1. PRL-425QRT-SMA Block Diagram
Fig 2. PRL-425QRT-RJRJ Block Diagram


Symbol Parameter Min Typ Max Unit Comments
RIND Differential Input Resistance 124 Ω
RINC Common Mode Input Resistance 5K Ω
IDC1 DC Input Current @ 50 MHz 265 280 mA
IDC2 DC Input Current @ 85 MHz 340 360 mA
VID Differential Input(1) V
VIA Single ended input(1) V
VCM Common Mode Input(1) -2.5 5.0 V
VDC DC Input Voltage 7.5 8.5 12.0 V
VAC AC/DC Adapter Input Voltage 103 115 127 V
VOHNL Output Hi Level, No Load 4.4 5.0 V RL=1 MΩ @ DC
VOHFL Output Hi Level, Full load 2.2 2.5 V RL=50 Ω @ DC
VOLNL Output Lo Level, No Load -0.1 0.0 0.4 V RL=1 MΩ @ DC
VOLFL Output Lo Level, Full Load -0.05 0.00 0.20 V RL=50 Ω @ DC
TPLH Propagation Delay to output ↑ 2.2 ns
TPHL Propagation Delay to output ↓ 2.2 ns
tr Rise Time (10%-90%) 1.8 2.5 ns
tf Fall Time (10%-90%) 1.8 2.5 ns
TSKEW Skew between any 2 outputs 250 600 ps
FMAX1 Max. Clock Frequency(2) 70 75 MHz
DTY Positive Duty Cycle @ 50 MHz 55 % ↑ Input
Size 1.3 x 2.9 x 2.9 in -SMA version
Size 1.3 x 2.9 x 3.9 in -RJRJ version
Weight, excluding AC adapter 5 Oz
Shipping weight, Including AC adapter 4 lb

(1): See Fig. 1