2 Phase NECL/TTL Frequency Divider


$ 1,581.25


  • System clock simulation
  • Low-jitter NECL/TTL clock source
  • SONET clock generator
  • Low-jitter Laser System Synchronization
  • Dividing Ti:S laser oscillator signals
  • A Mini Modular Instrument ™ for working with TTL/CMOS and ECL circuits
  • The PRL-260BNT replaces the discontinued PRL-260ANT


  • f/2 to f/4096, manually programmable
  • Common divider f/n (2 = n = 256) has 8-bit resolution
  • Φ1 output=(f/n)/(1, 2, 4 or 8), for max ratio of 2048
  • Φ2 output=(f/n)/(2, 4, 8 or 16), for max ratio of 4096
  • Φ1 has complementary NECL& TTL outputs and square wave outputs except when the final divisor is 1
  • Φ2 has complementary NECL square wave outputs
  • Single-ended NECL, differential NECL, or AC-coupled sinewave inputs with internal 50 Ω/VTT terminations
  • Additional logically-ORed TTL input requires only 0.7 V 
  • Small Signal Comparator Input requires only 40 mV
  • 20 ps typical edge jitter
  • 50 ps typical skew between f/n & f/n NECL outputs
  • 200 ps typical skew between f/n & f/n TTL outputs
  • 1.25 GHz typical max. external clock input frequency
  • Complementary NECL outputs drive 50 Ω loads terminated to VTT, AC-coupled or floating 50  Ω loads
  • Complementary TTL outputs drive long lines with or without 50 Ω load terminations
  • DC-coupled I/Os
  • SMA I/O connectors except for TTL/Small Signal Input (BNC)
  • Ready-to-use 1.3 x 2.9 x 6.1-in. module includes a ±8.5V AC/DC adapter


The PRL-260BNT is a DC-coupled, manually programmable, two-phase frequency divider with two sets of divided outputs, Φ1 and Φ2. It is capable of running at input clock frequencies in excess of 1 GHz and outputting divided TTL and NECL clock signals. The input frequency f is first divided down to f/n, where 2 ≤ n ≤ 256, via D1-D8 of a ten-bit DIP switch. The f/n signal is further divided by 1, 2, 4, or 8 for the Φ1 NECL and TTL outputs via D9 and D10, for a maximum ratio of 2048, and by 2, 4, 8 or 16 for the Φ2 NECL output via D11 and D12 of a second two-bit DIP switch, for a maximum ratio of 4096.

All outputs are synchronous with the input frequency and are square waves (50% duty cycle), except for Φ1 output when the final divisor is set to 1 (D9-D10=00). When the final divisor is set to 1 the output positive pulse width is equal to the input pulse period. All outputs are complementary and will drive long lines. TTL outputs are back-matched and will drive terminated or unterminated loads. NECL outputs can drive 50 Ω loads terminated into -2 V or AC-coupled 50 Ω loads.

A complementary NECL input is logically ORed with a TTL/Small Signal input, enabling the unit to accept TTL input, small signals (≥40 mV), single-ended or differential NECL input,  AC-coupled sinewave or other logic inputs. There is an Input Mode switch and a Threshold Voltage switch. For differential NECL inputs, both SMAs are used with both switches up. For single-ended NECL input the lower SMA is used with Input switch down and the Threshold switch up. For AC-coupled input either SMA can be used with both switches up. For TTL input the BNC input is used with the Input switch down and the Threshold switch up. For small signals the BNC input is used with both switches down.

The NECL inputs are internally terminated to 50 Ω/-2 V in the differential input mode, and the inverted input to 62 Ω/-1.3 V in the single-ended input mode. The BNC input has a ground-referenced 50 Ω termination, and the minimum signal required is only 0.75 V for TTL (switch up) or 40 mV for small signals (switch down):

Desired Input Connector(s) Input Mode Switch Threshold Switch
Differential NECL Both SMAs Up Up
Single-ended NECL Lower SMA Down Up
AC-coupled Either SMA Up Up
Small Signals BNC Down Down

The PRL-260BNT is ideal for applications where a frequency divider or prescalar is needed for triggering or down-sampling, and the multiple logic inputs and outputs make it extremely useful in mixed-logic environments. The two phases of output enable applications requiring two different ratios from a common reference frequency. Applications for the PRL-260BNT include data acquisition, test, measurement, R&D, and laser system synchronization.

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

The PRL-260BNT is an improved model of the discontinued PRL-260ANT. It has all the features of the PRL-260ANT plus a small-signal input. The PRL-260BNT is recommended for all new applications.


Symbol Parameter Min Typ Max Unit Comments
Rin External Clock Input Resistance 49.5 50.0 50.5 Except f input in single-ended mode
VTT External Clock Input Termination Voltage -2.2 -2.0
-1.8 V ECL input
TTL/Small Signal input
IDC DC Input Current   +165/
VDC DC Input Voltage ±7.5 ±8.5 ±12 V  
VAC AC/DC Adapter Input Voltage 103 115 127 V  
VIH External Clock Input Hi Level
(Rin terminated to VTT)
V NECL (VTT = -2 V)
TTL (VTT= 0 V)
Small Signal (VTT = 0 V)
VIL External Clock Input Lo Level
(Rin terminated to VTT)
V NECL (VTT = -2 V)
TTL (VTT= 0 V)
Small Signal (VTT = 0 V)
VOH Output Hi Level @100 MHz
(RL terminated to VTT)
-0.81 V NECL (VTT = -2 V)
TTL (VTT= 0 V)
VOL Output Lo Level @100 MHz
(RL terminated to VTT)
V NECL (VTT = -2 V)
TTL (VTT = 0 V)
tPLH1 Propagation Delay to f output ↑   2500   ps From Ext Clk input
tPLH2 Propagation Delay to NECL f/n output ↑   3750   ps From Ext Clk input
tPLH3 Propagation Delay to TTL f/n output ↑   2500   ps From Ext Clk input
tr/tf1 Rise/Fall Times (20%-80%), ECL outputs   600 700 ps Note (1)
tr/tf2 Rise/Fall Times (10%-90%), TTL outputs   1100 1350 ps  
tSKEW1 Skew ↔ Φ1 NECL outputs   50 150 ps  
tSKEW2 Skew ↔ Φ1 TTL outputs   200 400 ps  
tSKEW3 Skew ↔ Φ1 NECL and TTL outputs   1300 1600 ps  
tSKEW4 Skew ↔ Φ1 and Φ2 NECL outputs   50 150 ps n≠1
fMAX In Max input clock frequency 1000 1150  1500 MHz  
fMAX Out Max output frequency 500
  MHz NECL outputs
TTL outputs
  Size 1.3 x 2.9 x 6.1  in.  
  Weight 10 Oz  
  Shipping Weight 4 lbs  
*All dynamic NECL measurements are made with outputs terminated into 50 Ω/ VTT, using the PRL-550NQ4X, four channel NECL Terminator, connected to a 50 Ω input sampling oscilloscope. TTL outputs are terminated to 50 Ω.
(1). The output rise and fall times of each NECL channel are measured with its complementary output terminated into 50 Ω/ VTT. An unused complementary 50 Ω output must be either terminated into 50 Ω/ VTT or AC coupled into a 50 Ω load; otherwise, output waveform distortion and rise time degradation will occur. Use the PRL-ACT-50, Dual Ch. AC-Coupled 50 Ω Termination, for the 50 Ω/VTT termination. Use the PRL-SC-104 or PRL-ACX-12dB (0.1 µf DC block and 12 dB AC-coupled attenuator, respectively) for connection of NECL signals to 50 Ω input oscilloscopes.