The PRL-431AN is a 1:2 Differential Fanout NECL Buffer module. It is an essential lab tool for applications where it is necessary to drive two different loads from a single source of single-ended or differential NECL signals. It can also be used for converting GHz sine wave signals into two pairs of differential NECL signals.
A switch selects either single-ended or differential inputs, as shown in Fig. 1. In the differential input mode, both inputs D and D are terminated internally into 50 Ω/VTT*, and, therefore, either one or both inputs can accept AC-coupled signals as well. In the single input mode, signal should be connected to the D input only. The D input is switched internally to VBB**, and the termination resistor RT for the D input is changed to 62 Ω. Complementary outputs of the PRL-431AN are designed for driving 50 Ω loads terminated into -2 V. With internal pull-down resistors, these outputs can also be AC-coupled for driving 50 Ω loads terminated to ground or to other voltages.
Any single output from the PRL-431AN can drive a single-ended NECL input, but the complementary output should also be terminated into 50 Ω/VTT or AC coupled into 50 Ω/GND.
The PRL-431AN is housed in a 1.3 x 2.9 x 2.2-in. extruded aluminum enclosure and supplied with a ±8.5 V/1.8 A AC/DC Adapter.
VTT is nominally -2.0 V for ECL, +3.0 V for PECL, and +1.3 V for LVPECL. VBB is nominally -1.3 V for ECL, +3.7 V for PECL, and 2.0 V for LVPECL.
(0° C ≤ TA ≤ 35° C)*
|VTT||D Input Termination Voltage (fixed)||-2.2||-2.0||-1.8||V|
|VT1||D Input Termination Voltage||-2.2||-2.0||-1.8||V|
|VT2||D Input Termination Voltage (variable)||-1.17||-1.30||-1.43||V|
|VIL||Input Lo Voltage||-1.95||-1.60||-1.48||V|
|VIH||Input Hi Voltage||-1.13||-0.90||-0.81||V|
|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||-165||-180||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 output ↑||500||950||ps|
|tPHL||Propagation Delay to output ↓||500||950||ps|
|tr/tf||Rise/Fall Times (20%-80%)||250||ps||Note (1)|
|tSKEW||Skew between any 2 outputs||20||75||ps|
|fMAX||Max clock frequency||3.5||4.0||GHz||Notes (2)|
|VCMR||Common Mode Range||-2.7||-0.4||V|
|Size||1.3 x 2.9 x 2.2||in.|
|Weight, excluding AC adapter||5||Oz|
|Shipping weight, including AC adapter||4||lb.|
*All measurements are made with outputs terminated into 50 Ω/VTT, using the PRL-550NQ4X four channel NECL Terminators, connected to a 50 Ω input sampling oscilloscope.
(1). 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-550NQ4X, four channel NECL Terminator, for the 50 Ω/VTT termination and for connection of NECL 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.
(2). fMAX is measured by AC coupling a sine wave to the D input using the differential input mode (switch up). The differential outputs are first divided by four, using the PRL-255N and then measured using the PRL-550NQ4X, four channel NECL Terminator, connected to a sampling scope.