12 GHz Programmable 2-Phase Frequency Divider (f/8-f/128)


$ 1,614.60


  • 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


  • 12 GHz typical maximum External Clock Input frequency
  • f/8 to f/128 with independent 2Φ outputs
  • Common Divide by 8 pre-scalar for both Φ1 and Φ2
  • Φ1 output = (f/8)/(1, 2, 4 or 8), for max. ratio of 64
  • Φ2 output = (f/8)/(2, 4, 8 or 16), for max. ratio of 128
  • Both Φ1 and Φ2 have two pairs of complementary NECL square wave outputs
  • Single-ended AC Coupled Input with internal 50 Ω termination
  • 5 ps typical Edge Jitter
  • 40 ps typical skew between f/n & f/n NECL outputs
  • 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-257-8 is an AC-coupled input, manually programmable, two phase frequency divider with two sets of complementary NECL outputs. It is capable of running at input frequencies in excess of 12 GHz.

It has a common divide-by-8 pre-scalar front end followed by two banks of independent manually programmable dividers, Φ1and Φ2. The f/8 pre-scalar output is further divided by 1, 2, 4, or 8 for the Φ1 bank via D0 and D1 of a two-bit DIP switch, providing a maximum ratio of 64. It is divided by 2, 4, 8 or 16 for the Φ2 bank via D2 and D3 of a second two-bit DIP switch, providing a maximum ratio of 128. All outputs are synchronous with the input frequency and are square waves (50% duty cycle) suitable for driving long lines terminated into 50 Ω/-2 V or AC-coupled 50 Ω loads.

The PRL-257-8 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-257-8 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. 

Fig. 2: PRL-257-8 Block Diagram

Sample Applications and Test Results

The PRL-257-8 was reviewed by a well-respected member of the Signal Integrity mailing list:

". . . the device has a [specified] bandwidth up to 12GHz, and my measurements show that its actual bandwidth goes out to 14GHz.  I thought that was very good margin.  But what really impressed me was the jitter performance.  I fed in a clock source with 170fs one sigma RJ, and the clock divider puts out a divided down clock with 770fs one sigma RJ.  That is surprisingly good for a small device with such high bandwidth.  Usually you would expect this kind of performance from a device weighing 40 lb and takes up a whole lot of bench top space, but this clock divider is small enough to fit in your pocket."

The full review is available at the si-list archives

Scope shots from his testing are below:

Fig. 3: PRL-257-8 Output Waveform, 14 GHz input clock divided by 64

Fig. 4: PRL-257-8 Jitter Performance*, 10.3125 GHz clock divided by 8

Fig. 5: PRL-257-8 Jitter Performance*, 10.3125 GHz clock divided by 64

Fig. 6: PRL-257-8 Jitter Performance*, 2.125 GHz clock divided by 8

* These test results, though typical, are not guaranteed performance specifications.


Symbol Parameter PRL-257-8 Unit Comments
Min Typ Max
RIN Input Resistance   50   Ω AC Coupled
CC Coupling Capacitor 0.08 0.10 0.12 µf Input TC=50 µs
VINmin Minimum p-p Input Amplitude 500
Sine Wave@ FMIN In I
Square Wave, tr <2ns
Square Wave, tr <500ps
VINmax Maximum p-p Input Amplitude   2.00 1.25 V Sine or Square Wave
VOL Output Lo Voltage @ 100 MHz -1.95 -1.60 -1.48 V Output terminated to 50 Ω/-2V
VOH Output Hi Voltage @ 100 MHz -1.13 -0.90 -0.81 V Output terminated to 50 Ω/-2V
IDC1 DC Input Current, +8.5 V   +80 +100 mA  
IDC2 DC Input Current, -8.5 V -285 -300 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 Φ1 output ↑   2500   ps  
tPHL Propagation Delay to Φ1 output ↓   2500   ps  
tr/tf Rise/Fall Times (20%-80%)   200 250 ps Note (1)
tSKEW1 Skew↔ Φ1 or Φ2 outputs   40 120 ps  
tSKEW2 Skew↔ Φ1 and Φ2 outputs   40 120 ps D0/D1=10, D2/D3=00
  Jitter, p-p   5 10 ps Note (2)
FMIN In I Minimum Input frequency 120 100   MHz Sine wave input
FMIN In II Minimum Input frequency 150 100   KHz Square wave input
FMAX In I Maximum Input frequency 10.0 12.0 12.5 GHz  
FMAX Out1 Maximum Output frequency, Φ1 1.25 1.50 1.56 GHz Φ1 outputs
FMAX Out2 Maximum Output frequency, Φ2 0.625 0.750 0.780 GHz Φ2 outputs
  Size 1.3 x 2.9 x 2.9 in.  
  Weight, excl. AC adapter 10 Oz.  
  Shipping weight, incl. AC adapter 3 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 the PRL-ACX-12dB, 12 dB AC-coupled attenuator, may be used to connect the NECL/PECL/LVPECL outputs to 50 Ω input instruments.
Jitter specification limited by PRL internal test equipment. Independent testing shows typical jitter performance of < 1 ps one-sigma RJ.