2-Phase Programmable NECL Frequency Divider (f/1 - f/16)


$ 862.50


  • System Clock Simulation
  • Low Jitter NECL Clock Source
  • SONET Clock Generator
  • Laser Pump Synchronization
  • Scope triggering
  • PRBS/BERT synchronization
  • Optimizing outputs from frequency synthesizers
  • Testing high-speed serial/SERDES links (GB Ethernet, eSATA, PCIe, HT, etc)
  • An Essential Lab Tool for Working with NECL Circuits


  • 2+ GHz typical maximum External Clock Input frequency
  • f/1 - f/16 outputs with independent 2φ outputs
  • φ1 output = f/1, 2, 4 or 8
  • φ2 output = f/2, 4, 8 or 16
  • Both φ1 and φ2 have two pairs of complementary NECL outputs
  • Square wave outputs (except f/1)
  • Internal 50 Ω/-2V Input Terminations also accept AC-coupled PECL or sinewave signals
  • 10 ps typical Edge Jitter
  • 40 ps typical skew between f/n & f/n NECL outputs (each phase)
  • Complementary DC coupled NECL Outputs drive 50 Ω loads terminated to -2 V, AC coupled or floating 50 Ω loads
  • SMA I/O Connectors
  • Ready-to-Use 1.3 x 2.9 x 2.9-in. Module includes a ±8.5V AC/DC Adapter


The PRL-256N is a NECL input, manually programmable, two-phase frequency divider with four pairs of complementary NECL outputs, capable of running at input frequencies in excess of 2 GHz. The input selector switch selects either single-ended or differential inputs. In the differential input mode, both inputs CLK and CLK are terminated internally into 50 Ω/VTT, where VTT is equal to -2 V for NECL, and therefore, either one or both inputs can accept AC coupled signals as well. In the single input mode, input signals should be connected to the CLK input only. The CLK input is internally switched to VBB, nominally -1.3 V for NECL, and input resistor RT for the CLK input channel is changed to 62 Ω.

The input buffer is followed by two banks of independent manually programmable dividers, Φ1and Φ2. The input is divided by 1, 2, 4, or 8 for the Φ1 bank via D0 and D1 of a two-bit DIP switch. It is divided by 2, 4, 8 or 16 for the Φ2 bank via D2 and D3 of a second two-bit DIP switch. Each bank has two pairs of complementary outputs. All outputs are synchronous with the input frequency and are square waves (50% duty cycle) except for the f/1 outputs, which follow the input.

The outputs are suitable for driving long lines terminated into 50 Ω/-2 V or AC-coupled 50 Ω loads.

The PRL-256N is ideal for applications where a high-frequency divider or pre-scalar is needed for triggering or down-sampling. The two phases of output enable applications requiring two different ratios from a common reference frequency, and the 1:2 fanout feature enables system synchronization and monitoring/triggering applications from a single reference clock source. Applications for the PRL-256N include data acquisition, test, measurement, R&D, and system integration.

The unit includes an AC adapter for ready-to-use convenience on the bench or in a system. All I/O connectors are SMA. The extruded aluminum housing is suitable for mounting with the optional brackets.

PRL-256N Block Diagram


Symbol Parameter PRL-255N Unit Comments
Min Typ Max
RIN Input Resistance 49.5 50 50.5
VTT D Input Termination Voltage (fixed) -2.2 -2 -1.8 V CLK input
VT1 D Input Termination Voltage (switch Up) -2.2 -2.0 -1.8 V CLK input
VT2 D Input Termination Voltage (switch Down) -1.17 -1.30 -1.43 CLK input
VIL Input Lo Voltage -1.95 -1.60 -1.48 V
VIH Input Hi Voltage -1.13 -0.90 -0.81 V
SW VIN Sine wave Input, VPP 30 50 500 mV
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 -375 -350   mA
VDC DC Input Voltage -12 -8.5 -7.5 V
VAC AC/DC Adapter Input Voltage 103 115 127 V
tPLH Propagation Delay to output ↑   2500   ps
tPHL Propagation Delay to output ↓   2500   ps
tr/tf Rise/Fall Times (20%-80%)   200 300 ps
tSKEW1 Skew ↔ Φ1 or Φ2 outputs   40 120 ps
tSKEW2 Skew ↔ Φ1 and Φ2 outputs   40 120 ps D0/D1=10, D2/D3=00
tSKEW Skew between any two outputs   40   ps
FMAX Max clock frequency 2.0 2.5   GHz
Size 1.3 x 2.9 x 2.9 in.
Weight, excl. AC adapter 5 Oz.
Shipping weight, incl. AC adapter 4 lb.
* All measurements are made with outputs terminated into 50 Ω/VTT.
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-550 Series, four channel ECL/PECL/LVPECL Terminators, for the 50 Ω/VTT termination and for connection of ECL/PECL/LVPECL signals to 50 Ω input oscilloscopes. The PRL-ACT-50, Dual Channel AC-Coupled 50 Ω Terminator, may also be used to provide the 50 Ω/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.