Small Signal Freq. Divider (f/2, f/4), NECL Outputs


$ 1,490.40


  • GHz Frequency Division in Device Test and Systems Integration
  • High speed Clock signal Generation for SONET applications
  • An Essential Lab Tool for Working with GHz ECL Circuits


  • 2 GHz Toggle Frequency
  • Single-ended or Differential Inputs
  • Complementary NECL Outputs drive 50 Ω Loads terminated to -2 V
  • DC Coupled I/Os
  • SMA I/O Connectors
  • Ready-to-Use 1.3 x 2.9 x 3.9-in.Module includes a ±8.5 V AC/DC Adapter


The PRL-255CN is a dual-channel ÷2 and ÷4 frequency divider with DC-coupled, 50 Ω comparator inputs, and complementary NECL outputs. The maximum frequency of operation is greater than 2 GHz, and the minimum input signal required is 10 mVPP at 300 MHz. It is ideally suited for dividing mV sinewave signals or small pulses from laser oscillator photodiodes.

The two channels can be cascaded to provide a ÷8 function. The PRL-255CN is an essential lab tool for device test and systems integration in wireless and digital communications applications.

The comparator input threshold voltage for the PRL-255CN can be set to +50 mV, 0 V or -50 mV using the common three-position switch provided. It can also be varied independently in each channel by applying a DC bias voltage to one of the two inputs. In this case, a feed through decoupling capacitor of 0.1 µf, such as the PRL-FTC-104, is recommended for preventing false triggering or oscillation if the bias voltage contains varying components, such as noise. Input common mode range is -2.5 V to +4 V. To prevent oscillation in a non-driven channel when the preset threshold is set to 0 V, connect an output to an input so that the two inputs are not at the same voltage.

The PRL-255CN is housed in a 1.3 x 2.9 x 3.9-in. enclosure and supplied with a ±8.5 V/1.8 A AC/DC Adapter.

PRL-255CN Block Diagram


Symbol Parameter PRL-255CN Unit


Min Typ Max
RIN Input Resistance 49.5 50.0 50.5
VTH+ Preset Positive Threshold Voltage +40 +50 +60 mV
VTH- Preset Negative Threshold Voltage -60 -50 -40 mV
VTH 0 Preset Zero Threshold Voltage -5 0 +5 mV
VIN Min 1 Minimum Input Voltage p-p 10 5 mV 0 < f < 300 MHz
VIN Min 2 Minimum Input Voltage p-p 400 200 mV 300 MHz < f < 2.5 GHz
IDC DC Input Current +35
VDC DC Input Voltage ±7.5 ±8.5 ±12 V

AC/DC Adapter Input Voltage

103 115 127 V

Propagation Delay to output ↑

  1.8 2.2 ns

Propagation Delay to output ↓

  1.8 2.2 ns

Propagation Delay to output ↑

  2.0 2.5 ns

Propagation Delay to output ↓

  2.0 2.5 ns
tr/tf Rise/Fall Times (20%-80%)   400 600 ps Note (1)

Skew between Q& Q outputs

  50 150 ps  
FMAX Max clock frequency 2.0 2.5   GHz Note (3)
VCMR Common Mode Range -2.5   +4 V
Size 1.3 x 2.9 x 3.9 in.
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 forconnection 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/VTTtermination. 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.
(2). These parameters are not supplied by the device manufacturer and are, therefore, not guaranteed.
(3). fMAX is measured by AC coupling a sine wave to the ÷2 CLK input using the differential input mode (switch up). The ÷2 and the ÷4 dividers are cascaded, and the ÷8 outputs are then measured. The fMAX measurement is then repeated by clocking the ÷4 CLK input with the sine wave.