1:22 TTL Fanout Buffer/Line Driver


$ 4,465.45


  • TTL/CMOS Clock Distribution
  • 1:22 Fanout Line Driver
  • High Speed Digital Communications System Testing
  • 1 PPS Distribution/IRIG-B Distribution
  • Mini Modular Instrument


  • fMAX > 100 MHz
  • Drives 100 ft of cable @ 80 MHz
  • 1.8 ns Typical Output Rise & Fall Times
  • 2.5 V into 50 Ω Typical
  • TTL Compatible 50 Ω or 1 kΩ Input
  • Twenty in-phase 50 Ω TTL Outputs
  • Two auxiliary 50 Ω TTL Outputs suitable for cascading
  • Active Low EN (Enable) Inputs for each bank of 10 outputs
  • BNC or SMA I/O Connectors, plus two SMA auxiliary outputs
  • DC Coupled I/Os
  • Self-contained 3.0 x 6.8 x 4.0-in. unit includes an AC/DC Adapter


The PRL-4122-BNC is a 1:22 fanout, 50 Ω TTL Line Driver. It is intended for distribution of high-speed clock and logic signals to multiple loads via long lines. The 50 Ω back-terminated outputs can drive long lines with or without 50 Ω load terminations. With 50 Ω load terminations, however, all outputs of the PRL-4122 can drive 100 ft of 50 Ω cables at clock rates greater than 80 MHz.

The PRL-4122 is implemented as a 1:4 fanout buffer (equivalent to a PRL-414B module) with two of its outputs externally cabled to the inputs of two 1:10 fanout buffers (each equivalent to a PRL-4110 module). The twenty outputs from the two 1:10 modules are in phase, while the additional two outputs of the 1:4 module are advanced by approximately 10 ns. These auxiliary outputs can be used to drive the inputs of downstream PRL-4110 or PRL-4220 units for additional in-phase outputs.

The input resistance of the PRL-4122’s primary input can be selected to be either 50 Ω or 1 kΩ by a switch. The 1 kΩ-input is desirable when interfacing with low power circuits. The 50 Ω back terminated outputs typically deliver 2.5 V into 50 Ω or 5.0 V into Hi-Z loads. All I/Os are DC coupled and have BNC or SMA connectors, except for the auxiliary outputs which are SMA. 

Each 1:10 fanout bank also has an independent TTL-compatible EN input pulled down via a 1 kΩ resistor. When left open the Enable is active, and the fanout bank will output signals. Each bank can be disabled by driving its EN input high. A block diagram showing the equivalent input and output circuits of the PRL-4122 is shown in Fig. 1.

The PRL-4122 is housed in a 3.0 x 6.8 x 4.0-in. extruded aluminum enclosure and is supplied with the PRL-760E, ±8.5 V/±1.8 A AC/DC Adapter.

Related Products:

  • PRL-4110, 1:10 Fanout 50 Ω TTL Line Driver
  • PRL-4220, 2:20 Fanout 50 Ω TTL Line Driver, equivalent to two PRL-4110 units in a single enclosure
  • PRL-4330, 3:30 Fanout 50 Ω TTL Line Driver, equivalent to three PRL-4110 units in a single enclosure

(0° C ≤ TA ≤ 35° C)*

Symbol Parameter Min Typ Max Unit Comments
RIN LO Input Resistance Low Range 49.5 50 50.5
RIN HI Input Resistance High Range 9.9 10.0 10.1 kΩ
RIN EN Input Resistance, Enable   1   kΩ  
ROUT Output Resistance   50    
VIL TTL Input Low Level -0.5 0.0 0.5 V  
VIH TTL Input High Level 2.0 2.4 5.0 V  
VIL EN EN Input Low Level -0.5 0.0 0.5 V  
VIH EN EN Input High Level 2.0 2.4 5.0 V Drive EN High to disable output
VOL TTL Output Low Level 0.0 0.25 0.5 V RL=50 Ω
VOH1 TTL Output High Level 2.2 2.5   V RL=50 Ω @ DC
VOH2 TTL Output High Level 4.4 5.0   V RL=1 MΩ @ DC
IDC1 DC Input Current   1220   mA F =50 MHz sq. wave(1)
IDC2 DC Input Current   1510   mA F ≤ 100 MHz
IDC3 DC Input Current     1800 mA F =125 MHz
VDC DC Input Voltages 7.75 8.50 12.00 V  
VAC AC/DC Adapter Input Voltage 103 115 127 V  
TPLH1 Propagation Delay to output ↑   19 22 ns For 1:20 primary outputs
TPHL1 Propagation Delay to output ↓   19 22 ns For 1:20 primary outputs 
TPLH2 Propagation Delay to output ↑   10 12 ns For 2 auxiliary outputs
TPHL2 Propagation Delay to output ↓   8 12 ns For 2 auxiliary outputs
tr Rise Time (10%-90%)   1.8 2.5 ns  
tf Fall Times (10%-90%)   1.5 2.5 ns  
TSKEW1 Skew between any 2 outputs   500 900 ps Within one 1:10 bank
TSKEW2 Skew between any 2 outputs   1200 1600 ps Any two primary outputs
FMAX1 Max. Clock Frequency(2) 100 125   MHz RG58C/U, cable length =3 ft
FMAX2 Max. Clock Frequency(3)   80     RG58C/U, cable length = 100 ft
PWMIN1 Minimum Pulse Width   4   ns ↑ Input
PWMIN2 Minimum Pulse Width   6   ns ↓ Input
  Size 3.0 x 6.8 x 4.0 in  
  Weight 2 lb Excluding AC adapter
  Shipping Weight 6 lb Including AC adapter
1. Power dissipation includes all three internal boards with all outputs terminated into 50 Ω. Each 1:10 board draws 725 mA maximum. The 1:4 board is powered internally from the bottom 1:10 board and draws 350 mA maximum.
2. fMAX should not exceed 125 MHz, otherwise damage of the unit due to overheating may result.
3. fMAX2 is measured by driving a PRL-414B at the end of a 100 ft cable.