ST2R509B

Overview

The Littelfuse ST2R509B is a leaded inrush current limiter (ICL) designed for AC-input power supplies. It features a nominal resistance of 2.5 Ohms with a tolerance of ±20%. The device has a maximum steady-state current rating of 9 A and a diameter of 0.900 inches (22.86 mm). Lead spacing is specified at 0.31 inches. This component serves as a series protection element to manage initial surge currents.

Feature Summary

• Provides series inrush current limiting for AC-input power supplies
• Designed for applications with large input capacitance
• Reduces stress on rectifiers and capacitors during startup

Applications

• Mains switch-mode power supplies (SMPS)
• AC-input power supplies with large input capacitance
• Power adapters requiring inrush current management

Procurement Notes

Verify the specific part number ST2R509B against official Littelfuse documentation to confirm active status and RoHS compliance details, as availability information may vary. Ensure that the 2.5 Ohm resistance and 9 A current ratings align with the target circuit design requirements before procurement.

Selection Notes

Select this component when designing AC-input power supplies that require passive inrush current limiting. Consider the 2.5 Ohm resistance value and 9 A continuous current rating to ensure compatibility with the system's electrical parameters and thermal environment.

Part Context

The ST2R509B belongs to the Littelfuse Inrush Current Limiter (ICL) product line. These components are categorized under Circuit Protection within the Power product family. They are distinct from TVS diodes and fuses, serving specifically to limit high initial currents during power-up phases.

Replacement Considerations

Public confirmed substitute part numbers are not available in the provided source material. Consult Littelfuse technical support or authorized distributors for equivalent ICL components with matching resistance and current ratings.