1:4 LVDS Fanout Buffer, NECL and TTL Inputs


$ 1,029.25


  • LVDS Fanout Buffer
  • Converting NECL or Sinewave Signals to LVDS
  • Converting TTL Signals to LVDS
  • High Speed Digital Communications Systems Testing
  • Satellite Telemetry/Ground Station System Integration 


  • fMAX > 1.25GHz for NECL, > 300 MHz for TTL input
  • Single-ended or Differential NECL Input with Internal 50 Ω/VTT Input Termination also accepts Sinewave or AC-coupled Signals
  • Separate TTL input (1 V minimum) Logically ORed with NECL Inputs
  • 4 Pairs of Complementary 50 Ω LVDS Outputs
  • 500 ps Typical Output Rise & Fall Times
  • SMA Connectors for NECL Inputs
  • BNC Connector for TTL Input
  • SMA Output Connectors
  • Self-contained 1.3 x 2.9 x 5-in. unit includes ±8.5 V/1.8 A AC/DC Adapter


The PRL-424NLV is a 1:4 fanout, complementary output, LVDS line driver. It is intended for converting NECL signals, AC-coupled sine waves, or TTL signals into multiple LVDS signals for driving long lines. The PRL-424LV high speed fanout line driver facilitates testing of high speed digital communications circuits and distribution of satellite signals.

The PRL-424NLV has two logically ORed input circuits:

  • For the NECL input 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, where VTT is –2 V for NECL. In the differential input mode, therefore, either one or both inputs can accept AC coupled signals as well(1). In the single-ended input mode, signals should be connected to the D input only. The D input is switched internally to VBB, nominally -1.3 V for NECL, and termination resistor RT for the D input channel is changed to 62 Ω. The connectors for the NECL input are SMA.

  • The TTL input has a 50 Ω input termination with a minimum 1 V triggering threshold. The TTL input connector is BNC. When using the TTL input the NECL input selector switch should be in the Down position to prevent spurious triggering.

The four pairs of complementary outputs are 50 Ω back-terminated and are designed for driving floating 100 Ω loads, normally the configuration used in LVDS input circuits. The output swing is typically 600 mV with a common mode voltage of 1.2 V. All output connectors are SMA.

The PRL-424NLV is supplied with a ±8.5 V/1.8 A AC/DC adapter and housed in a 1.3 x 2.9 x 5-in. extruded aluminum enclosure. Available accessories include voltage distribution modules and brackets for mounting multiple units.

(1) A related model, the PRL-424LV, has a "universal differential" input (floating 100 Ω termination) that will accept LVDS, RS-422, NECL and LVPECL, so long as the NECL and LVPECL signals are differential and have internal pull-down resistors.
Fig. PRL-424NLV Block Diagram

(0° C ≤ TA ≤ 35° C)*

RIN Input Resistance 49.5 50 50.5  
VTT D Input Termination Voltage (fixed) -2.2 -2.0 -1.8 V  
VT1 D Input Termination Voltage -1.17 -1.30 -1.43 V  Switch Down
VT2 D Input Termination Voltage -2.20 -2.00 -1.80 V Switch Up 
VIL Input Lo Voltage -1.95 -1.60 -1.48 V  
VIH Input Hi Voltage -1.13 -0.90 -0.81 V  
VOL Output Low Level   0.9   V  
VOH Output High Level   1.5   V  
VIL Input Lo Voltage -1.95 -1.60 -1.48 V  
IDC1 DC Input Current, +8.5 V   130 140 mA  
IDC2 DC Input Current, -8.5 V   -470 -480 mA  
VDC DC Input Voltage ±7.5 ±8.5 ±12 V  
VAC1 AC/DC Adapter Input Voltage, 120 103 115 127 V  
VAC1 AC/DC Adapter Input Voltage, 220 206 220 254 V  
tPLH Propagation Delay to output ↑   2.7   ns  
tPHL Propagation Delay to output ↓   2.7   ns  
tr/tf1 Rise/Fall Times (10%-90%)1   500 650 ps @ 200 MHz
tr/tf2 Rise/Fall Times (10%-90%)1   250   ps @ 1.25 GHz
tSKEW Skew between any 2 outputs   200 550 ps  
fMAX1 Max Clock Frequency, SMA Input2 1.25 1.35   GHz  
fMAX2 Max Clock Frequency, TTL Input 300   MHz  
  Size 1.3 x 2.9 x 5.0 in.  
  Weight 8 Oz  
  Shipping Weight 4 lbs  
(1) Rise and Fall times are measured with ground-referenced 50 Ω loads.
(2) fmax is measured using the PRL-174ANT Clock Driver outputs as the driver and the PRL-425N with SMA input connectors as the receiver. The outputs of the PRL-425N are then measured. fmax for the TTL input is currently limited by the lack of TTL drivers faster than 300 MHz.