1:2 Differential NECL Fanout Buffer, SMA I/Os


$ 914.25


  • Fanout Single-ended Input signals into two pairs of Differential signals for driving long lines
  • Ideal for receiving signals from long lines
  • Fanout GHz Sinewave signals into two pairs of Differential NECL signals
  • 1 PPS Distribution/IRIG-B Distribution
  • An Essential Lab Tool for Working with NECL Circuits


  • 4 GHz fMAX
  • Single-ended or Differential Inputs
  • Internal 50 Ω/VTT Input Terminations also accept AC coupled Signals
  • Complementary Outputs drive 50 Ω loads terminated to VTT
  • DC Coupled I/Os Compatible with ECLinPS or 10KH Devices
  • SMA I/O Connectors
  • Ready-to-Use 1.3 x 2 9 x 2 2-in. Module includes a ±8.5 V AC/DC Adapter


The PRL-431AN is a 1:2 Differential Fanout NECL Buffer module. It is an essential lab tool for applications where it is necessary to drive two different loads from a single source of single-ended or differential NECL signals. It can also be used for converting GHz sine wave signals into two pairs of differential NECL signals.

A switch selects either single-ended or differential inputs, as shown in Fig. 1. In the differential input mode, both inputs D and D are terminated internally into 50 Ω/VTT*, and, therefore, either one or both inputs can accept AC-coupled signals as well. In the single input mode, signal should be connected to the D input only. The D input is switched internally to VBB**, and the termination resistor RT for the D input is changed to 62 Ω. Complementary outputs of the PRL-431AN are designed for driving 50 Ω loads terminated into -2 V. With internal pull-down resistors, these outputs can also be AC-coupled for driving 50 Ω loads terminated to ground or to other voltages.

Any single output from the PRL-431AN can drive a single-ended NECL input, but the complementary output should also be terminated into 50 Ω/VTT or AC coupled into 50 Ω/GND.

The PRL-431AN is housed in a 1.3 x 2.9 x 2.2-in. extruded aluminum enclosure and supplied with a ±8.5 V/1.8 A AC/DC Adapter.

VTT is nominally -2.0 V for ECL, +3.0 V for PECL, and +1.3 V for LVPECL. VBB is nominally -1.3 V for ECL, +3.7 V for PECL, and 2.0 V for LVPECL.

Fig 1, PRL-431AN Block Diagram

(0° C ≤ TA ≤ 35° C)*

Symbol Parameter PRL-431AN UNIT Comments
Min Typ Max
Rin Input Resistance 49.5 50.0 50.5  
VTT D Input Termination Voltage (fixed) -2.2 -2.0 -1.8 V  
VT1 D Input Termination Voltage -2.2 -2.0 -1.8 V  
VT2 D Input Termination Voltage (variable) -1.17 -1.30 -1.43 V  
VIL Input Lo Voltage -1.95 -1.60 -1.48 V  
VIH Input Hi Voltage -1.13 -0.90 -0.81 V  
VOL Output Lo Voltage -1.95 -1.70 -1.48 V  
VOH Output Hi Voltage -1.13 -0.90 -0.81 V  
IDC DC Input Current   -165 -180 mA  
VDC DC Input Voltage -7.5 -8.5 -12 V  
VAC AC/DC Adapter Input Voltage 103 115 127 V  
tPLH Propagation Delay to output ↑   500 950 ps  
tPHL Propagation Delay to output ↓   500 950 ps  
tr/tf Rise/Fall Times (20%-80%)   250 ps Note (1)
tSKEW Skew between any 2 outputs   20 75 ps  
fMAX Max clock frequency 3.5 4.0   GHz Notes (2)
VCMR Common Mode Range -2.7   -0.4 V  
  Size 1.3 x 2.9 x 2.2 in.  
  Weight, excluding AC adapter 5 Oz  
  Shipping weight, including AC adapter 4 lb.  

*All measurements are made with outputs terminated into 50 Ω/VTT, using the PRL-550NQ4X four channel NECL Terminators, connected to a 50 Ω input sampling oscilloscope.


(1). The output rise and fall times are measured with with all inputs terminated into 50 Ω/VTT. For best performance all outputs should be terminated into 50 Ω/VTT or else AC- coupled into 50 Ω loads. If a single output is used, its complement must be terminated; otherwise output waveform distortion will occur. If one pair of complementary outputs is used, the other complementary pair may remain unterminated. Use the PRL-550NQ4X, four channel NECL Terminator, for the 50 Ω/VTT termination and for connection of NECL signals to 50 Ω input oscilloscopes. The PRL-ACT-50, Dual Channel AC-Coupled 50  Terminator, may also be used to provide the 50 /VTT termination. If preservation of DC levels is not required, then the PRL-SC-104, 0.1 µf DC block or a 12 dB AC-coupled attenuator may be used to connect the NECL/PECL/LVPECL outputs to 50 Ω input instruments.

(2). fMAX is measured by AC coupling a sine wave to the D input using the differential input mode (switch up). The differential outputs are first divided by four, using the PRL-255N and then measured using the PRL-550NQ4X, four channel NECL Terminator, connected to a sampling scope.

VTT is nominally -2.0 V for ECL, +3.0 V for PECL, and +1.3 V for LVPECL. VBB is nominally -1.3 V for ECL, +3.7 V for PECL, and 2.0 V for LVPECL