ST1R030B

Overview

The Littelfuse ST1R030B is a radial leaded inrush current limiter (ICL) utilizing negative temperature coefficient (NTC) thermistor technology. It features a nominal resistance of 1 Ohm with a tolerance of ±20% and a continuous current rating of 30 Amperes. The component measures 0.75 inches (19.05 mm) in diameter with a lead spacing of 0.31 inches (7.87 mm). Designed for high-energy applications, it limits peak charging currents during power-up sequences to protect downstream circuitry from thermal stress.

Feature Summary

• Provides effective limitation of inrush current during initial power application
• Utilizes NTC thermistor material for automatic resistance adjustment based on temperature
• Radial leaded construction facilitates through-hole printed circuit board mounting

Applications

• Power supply input stages
• Motor drive circuits
• Transformer primary side protection

Procurement Notes

Verify the specific datasheet revision and RoHS compliance status directly with Littelfuse or authorized distributors prior to procurement. Confirm that the ambient operating temperature range aligns with the system's thermal environment. Ensure the physical dimensions and lead spacing match the target PCB footprint requirements to prevent mechanical assembly issues.

Selection Notes

Select this component when the circuit requires robust inrush current suppression at high continuous current levels. The 1 Ohm resistance value is suitable for moderate impedance requirements. Evaluate the steady-state heat dissipation capabilities of the PCB layout, as the device generates significant heat during normal operation due to its low resistance profile.

Part Context

This part belongs to Littelfuse’s ST series of inrush current limiters. These devices are engineered to replace traditional resistors or relay-based solutions by offering passive, maintenance-free protection against capacitive charging spikes. The series provides various resistance and current ratings to accommodate different power levels.

Replacement Considerations

Direct substitutes must match the 1 Ohm resistance, 30A current rating, and radial package style. Verify that alternative NTC thermistors have compatible maximum energy absorption ratings and steady-state current handling capabilities to ensure equivalent circuit protection performance.