B57211P0121M301

Overview

The B57211P0121M301 is a leaded inrush current limiter (NTC thermistor) manufactured by EPCOS, now part of TDK Electronics. It features a nominal resistance of 120 ohms at 25°C with ±20% tolerance and supports a maximum steady-state current of 1.5A. The component has a physical size of 13mm (0.512 inches). At operating temperature, the resistance drops to approximately 1.152 ohms. This NTC thermistor is designed for applications requiring effective suppression of initial surge currents during power-up sequences.

Feature Summary

• Provides effective suppression of inrush current during power-on events
• Utilizes negative temperature coefficient characteristics for automatic resistance adjustment
• Features a robust leaded construction suitable for through-hole mounting

Applications

• Power supply input stages
• Consumer electronic device protection
• Industrial equipment surge mitigation

Procurement Notes

Verify the manufacturer designation carefully, as EPCOS passive components have been rebranded under TDK Electronics. Confirm that the specific ordering suffix matches the required resistance and current ratings. Ensure the procurement documentation reflects the current brand identity to avoid confusion with legacy stock or obsolete listings.

Selection Notes

Select this component based on the required nominal resistance value and the maximum steady-state current rating of the circuit. Consider the thermal environment and the expected inrush current magnitude to ensure the thermistor can handle the energy dissipation without damage. Verify compatibility with the PCB footprint and lead spacing requirements.

Part Context

This component belongs to the B57211 series of NTC inrush current limiters. The series offers various resistance values and current ratings to suit different power levels. As part of the TDK portfolio following the acquisition of EPCOS, these components are widely used for protecting sensitive electronics from voltage spikes and high initial currents.

Replacement Considerations

Public confirmed substitute part numbers: None identified.