1:8 Diff. Fanout Buffer, Univ. Diff./TTL Input, LVDS Output


$ 2,012.50


  • 1:8 Fanout Buffer
  • Converting Differential NECL/LVPECL/RS-422 or TTL Signals to LVDS
  • Long Line Driver/Level Translator
  • Reference Clock Distribution/Translation
  • 1 PPS Distribution/IRIG-B Distribution
  • Telemetry and Avionics Distribution
  • Test and System Integration


  • fmax > 150 MHz for Differential Inputs
  • fmax > 100 MHz for TTL inputs
  • 1.2 ns Typical Rise & Fall Times for LVDS
  • Channel-to-channel skew less than 500 ps
  • Floating 100 Ω Universal Differential Inputs Accept LVDS, LVPECL, NECL, or RS-422 Inputs*
  • Separate TTL input (1 V minimum) Logically ORed with the Floating Differential Input
  • 8 Complementary Outputs
  • SMA or Triax Connectors for LVDS/LVPECL/NECL Inputs, BNC Connectors for TTL Input
  • SMA, BNC, or Triax Output Connectors
  • Self-contained 3.0H x 6.8W x 7.3L-in. unit includes ±8.5V/1.8A AC/DC Adapter
  • The related PRL-4216U series permits simultaneous CLK/DATA fanout with low skew


The PRL-4108UL is a series of 1:8 fanout differential line driver modules. All models have a floating 100 Ω universal differential input suitable for accepting LVDS, LVPECL, NECL, or RS422 signals.(1) They also have a logically ORed, 50 Ω TTL input with a minimum 1.0 V triggering threshold. Because the inputs are ORed a Hi level applied to either input can be used as a gate signal. Please see the block diagrams for more details.

The output is LVDS, available either with dual SMA connectors per differential output or one Triax connector per differential output.

The PRL-4108UL high speed fanout line driver facilitates testing of high speed digital communications circuits and distribution of satellite or telemetry signals. The product suffix specifies the input and output connectors, e.g. BNC, SMA, or TR (Triax):

Suffix Differential
Each Differential
-TR Triax BNC Triax


For example, model PRL-4108UL-SMA has SMA differential I/O connectors, while PRL-4108UL-TR has Triax differential I/O connectors. The TTL input connector is always BNC, and the differential input connectors can be SMA or Triax. Additional connector and output logic options may be available upon special order.

The floating differential input accepts differential LVDS, LVPECL, NECL, RS422, or any 75 mV minimum differential signal within a common-mode range of -2.0 V to +3.0 V. When driven by LVPECL or NECL inputs, these signals must have internal 150 Ω pull-up or 200 Ω pull down resistors, respectively (known as a "source-biased" output). The PRL-4108UL differential input is compatible with all LVPECL or NECL output signals from the PRL family of products.

The TTL input has a selectable 50 Ω/1 kΩ input load and will trigger on a minimum 1.0 V threshold. The 1 kΩ is useful for interfacing with low-power circuits.

The eight pairs of complementary outputs are back-terminated and are designed for driving long lines. See the Specifications page for output levels.

The PRL-4108UL is supplied with a ±8.5 V/1.8 A AC/DC Adapter and housed in a 3.0 x 6.8 x 6.0-in. extruded aluminum enclosure. Available accessories include voltage distribution modules and mating cables.

(1) A related series, the PRL-4108NL, has a true NECL input terminated into 50 Ω/-2 V, and can accept single-ended or differential NECL signals that do not have internal pull-downs.

Fig. 1B: PRL-4108UL-TR Simplified Block Diagram

(0° C ≤ TA≤ 35° C)*

Unless otherwise specified, dynamic measurements are made with all rear-panel outputs terminated into floating 124 Ω, using 124 Ω shielded twisted pair Triax cables (Trompeter P/N PCGOW10PCG-36 or equivalent). Channel to channel skew and propagation delay measurements are made using a PRL-425NTR Differential Receiver with NECL outputs. Rise and fall time measurements are made using a Triax to SMA adapter and connecting the SMA outputs to a 50 Ω input scope.
Min Typ Max
RT1-1 Differential Input Resistance 95 100 105
RINC Common Mode Input Resistance 5 kΩ
RT2-1 Input Resistance, TTL 50 Ω 49 50 51
RT2-2 Input Resistance, TTL 1 kΩ 0.95 1.00 1.05 kΩ
VCMR Input Common Mode Voltage -2.0 3.0 V
VIH1 TTL Input Hi Level 1.0 5.0 V Internally limited to 3.5V
VIL1 TTL Input Lo Level -0.5 0.5 V
ROUT1 Output Resistance 49.5 50.0 50.5 Single-ended
ROUT2 Output Resistance 99 100 101 Differential
VOH1 Output High Level 1.8 V No Load
VOH2 Output High Level 1.65 V Terminated to 124 Ω
VOL1 Output Low Level 0.78 V No Load
VOL2 Output Low Level 0.95 V Terminated to 124 Ω
VAC1 AC Adapter Input Voltage, 120 108 115 127 V
VAC2 AC Adapter Input Voltage, 220 216 230 254 V
IDC1 DC Input Current, +8.5 V Supply 385 mA
IDC2 DC Input Current, -8.5 V Supply -700 mA
tPROP1 Prop. Delay to Output ↑, Diff. Input 2.5 ns
tPROP2 Prop. Delay to Output ↑, TTL Input, 50 Ω 3.0 ns
tR Rise Time (10%-90%) 1.2 1.8 ns See Note 1
tF Fall Time (10%-90%) 1.2 1.8 ns See Note 1
tSKEW1 Ch./Ch. skew ↔ any 2 ↑ or 2 ↓ VO 200 350 ps
tSKEW2 Ch./Ch. skew ↔ any ↑ and ↓ VO 700 1200 ps
fMAX1 Max Clock Frequency, Diff. Input 150 175 MHz
fMAX2 Max Clock Frequency, TTL Input 100 125 MHz
Size 3.0”H x 6.8”W x 7.3”L in Including connectors
Weight 2 lbs Excluding AC adapter
Shipping weight 6 lbs Including AC adapter

Please contact sales@pulseresearchlab.com for performance specifications on other models.

(1) Due to lack of suitable equipment with floating differential 124 Ω input termination, tR and tF are measured using a 50 Ω input scope.