30R400UMR

Ptc Resettable Fuses Overview

The Littelfuse 30R400UMR is a PolySwitch resettable PTC fuse designed for overcurrent protection. It features a maximum voltage rating of 30 VDC and a hold current of 4 A. The device trips at 8 A and supports a maximum fault current of 40 A. Initial resistance is typically 50 mOhms, rising to a maximum of 200 mOhms after tripping. It operates within a temperature range of -40°C to +85°C and dissipates up to 2.5 W. The component utilizes radial leads with a 5.1 mm spacing and is supplied in tape and reel packaging.

Ptc Resettable Fuses Feature Summary

• Provides reliable overcurrent protection by increasing resistance as it heats during fault conditions
• Automatically resets to low resistance state once the fault is removed and the device cools
• Offers compact radial leaded form factor suitable for through-hole PCB mounting

Ptc Resettable Fuses Applications

• Protection of circuits, wiring harnesses, and PCB components from overcurrent events
• Overcurrent protection for automotive actuators, screens, and small motors
• Telecom and networking equipment protection against high-voltage fault currents

Ptc Resettable Fuses Procurement Notes

Verify that the ordering suffix 'UMR' corresponds to the specific tape and reel packaging configuration required for automated assembly processes. Confirm that the 30V DC voltage rating and 4A hold current align with the circuit's operational parameters. Ensure compatibility with the specified 5.1 mm lead spacing for the target PCB footprint. Cross-reference the RoHS compliance status and agency approvals such as UL and TUV with the latest official datasheet documentation before finalizing procurement.

Ptc Resettable Fuses Selection Notes

Select this component when a resettable solution is preferred over one-time fuses to maintain system availability after transient faults. The 30V rating limits its use to low-voltage DC applications. The 4A hold current must exceed the normal operating current while remaining below the trip threshold. Consider the thermal environment, as ambient temperature affects the hold current performance. The radial package is suitable for manual or wave soldering if not using automated pick-and-place equipment.

Ptc Resettable Fuses Part Context

The 30R400UMR belongs to the Littelfuse POLYFUSE 30R series of resettable polymeric positive temperature coefficient devices. This series is engineered for standard overcurrent protection duties in consumer electronics and industrial applications. The 30R designation indicates a 30V maximum working voltage class. These devices serve as solid-state alternatives to traditional fusible links, offering repeated protection cycles without replacement.

Ptc Resettable Fuses Replacement Considerations

The 30R400U is a bulk-packaged variant of the same electrical specification. Verify that the change in packaging from tape and reel to bulk does not impact the manufacturing assembly process.