ST5R004B

Overview

The ST5R004B is a radial lead inrush current limiter (ICL) manufactured by Littelfuse Inc. It features a nominal resistance of 5 Ohms with a tolerance of ±20% at 25°C. The device is rated for a steady-state current of 4 Amperes and has a body diameter of 15.24 mm (0.600 inches). The component utilizes a lead spacing of 7.62 mm (0.300 inches) for through-hole mounting. It complies with RoHS standards and is lead-free.

Feature Summary

• Provides high initial resistance to limit inrush current during power-up
• Automatically reduces resistance as temperature increases during operation
• Radial lead configuration facilitates easy through-hole PCB integration

Applications

• Power supply input stages
• Transformer primary circuits
• Capacitive load protection

Procurement Notes

Verify the specific Littelfuse datasheet for thermal characteristics and derating curves before finalizing designs. Confirm that the 4A steady-state rating aligns with the application's continuous current requirements. Ensure the 5 Ohm cold resistance meets the inrush limiting specifications. Check for any recent package or specification updates on the manufacturer's official website.

Selection Notes

Select this component when a fixed resistance value is required for inrush limiting rather than a resettable PTC. The 5 Ohm resistance and 4A current rating define the specific circuit constraints. Consider the physical size of the 15.24mm diameter for board space allocation. Evaluate the thermal environment to ensure the device operates within its safe operating area.

Part Context

This part belongs to the ST series of inrush current limiters, which are thermistors designed to protect electronic circuits from high surge currents. These components are distinct from fuses and standard resistors, serving specifically to manage transient energy during system startup phases in various industrial and consumer electronics applications.

Replacement Considerations

Consult Littelfuse documentation for direct cross-reference equivalents. Verify that any substitute maintains the 5 Ohm resistance and 4A current rating. Ensure the replacement matches the radial lead pitch and diameter dimensions for mechanical compatibility.