1:4 LVDS Fanout Buffer with NECL and TTL Inputs

Applications:

• LVDS Fanout Buffer
• Converting NECL or Sinewave Signals to LVDS
• Converting TTL Signals to LVDS
• High Speed Digital Communications Systems Testing
• Satellite Telemetry/Ground Station System Integration 

Features:

• f_MAX > 1.25GHz for NECL, > 300 MHz for TTL input
• Single-ended or Differential NECL Input with Internal 50 Ω/V_TT Input Termination also accepts Sinewave or AC-coupled Signals
• Separate TTL input (1 V minimum) Logically ORed with NECL Inputs
• 4 Pairs of Complementary 50 Ω LVDS Outputs
• 500 ps Typical Output Rise & Fall Times
• SMA Connectors for NECL Inputs
• BNC Connector for TTL Input
• SMA Output Connectors
• Self-contained 1.3 x 2.9 x 5-in. unit includes ±8.5 V/1.8 A AC/DC Adapter

Description

The PRL-424NLV is a 1:4 fanout, complementary output, LVDS line driver. It is intended for converting NECL signals, AC-coupled sine waves, or TTL signals into multiple LVDS signals for driving long lines. The PRL-424LV high speed fanout line driver facilitates testing of high speed digital communications circuits and distribution of satellite signals.

The PRL-424NLV has two logically ORed input circuits:

• For the NECL input 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/V_TT, where V_TT is –2 V for NECL. In the differential input mode, therefore, either one or both inputs can accept AC coupled signals as well⁽¹⁾. In the single-ended input mode, signals should be connected to the D input only. The D input is switched internally to V_BB, nominally -1.3 V for NECL, and termination resistor R_T for the D input channel is changed to 62 Ω. The connectors for the NECL input are SMA.

• The TTL input has a 50 Ω input termination with a minimum 1 V triggering threshold. The TTL input connector is BNC. When using the TTL input the NECL input selector switch should be in the Down position to prevent spurious triggering.

The four pairs of complementary outputs are 50 Ω back-terminated and are designed for driving floating 100 Ω loads, normally the configuration used in LVDS input circuits. The output swing is typically 600 mV with a common mode voltage of 1.2 V. All output connectors are SMA.

The PRL-424NLV is supplied with a ±8.5 V/1.8 A AC/DC adapter and housed in a 1.3 x 2.9 x 5-in. extruded aluminum enclosure. Available accessories include voltage distribution modules and brackets for mounting multiple units.

(1) A related model, the PRL-424LV, has a “universal differential” input (floating 100 Ω termination) that will accept LVDS, RS-422, NECL and LVPECL, so long as the NECL and LVPECL signals are differential and have internal pull-down resistors.