ST4R005B

Overview

The ST4R005B is a power thermistor manufactured by Littelfuse Inc., designed specifically for inrush current limiting applications. This component belongs to the ST Series of specially formulated NTC thermistors. It features a nominal resistance of 4 Ohms with a tolerance of ±20%. The device supports a maximum steady-state current of 5 A and has a diameter of 16.51 mm (0.650 inches). These specifications define its electrical and physical parameters for circuit protection roles.

Feature Summary

• Specially formulated NTC thermistor construction optimized for inrush current control
• Provides effective limitation of high initial charging currents in electronic circuits

Applications

• Inrush current limiting in power supply inputs
• Protection of capacitive loads during startup
• Circuit protection within consumer electronics assemblies

Procurement Notes

Verify the specific Littelfuse datasheet revision when sourcing this component to ensure alignment with current manufacturing standards. Confirm that the radial lead configuration matches the target PCB layout requirements. Cross-reference the 4 Ohm resistance value against the design schematic to prevent mismatched impedance characteristics in the final assembly process.

Selection Notes

Select this part based on the required 4 Ohm nominal resistance and 5 A current handling capability. Ensure the 16.51 mm diameter fits the available board space constraints. Evaluate the thermal environment to confirm the thermistor can dissipate heat effectively during steady-state operation without exceeding safe operating temperatures for the surrounding components.

Part Context

This component is part of the Littelfuse ST Series, which specializes in power thermistors for inrush current limiting. The series utilizes NTC technology to manage surge currents in various electronic systems. The ST4R005B represents a standard radial lead option within this family, providing reliable protection for general-purpose power applications requiring controlled current ramp-up.

Replacement Considerations

Consult official Littelfuse documentation for verified substitute part numbers within the ST Series or equivalent product lines. Do not assume cross-compatibility with generic NTC thermistors due to specific formulation differences. Verify that any alternative component meets the same 4 Ohm resistance and 5 A current ratings.