S4008FS21

Overview

The Littelfuse S4008FS21 is a sensitive silicon-controlled rectifier (SCR) from the Teccor line, designed for half-wave unidirectional gate-controlled rectification. It features an electrically isolated TO-220 package with a maximum on-state current of 8 A and a repetitive peak off-state voltage rating of 400 V. The device utilizes glass-passivated junctions to ensure long-term reliability and parameter stability against contamination. Key electrical specifications include a DC gate trigger current of 200 µA, a peak one-cycle forward surge current of 100 A, and a typical peak on-state voltage of 1.6 V at rated conditions.

Feature Summary

• Electrically isolated TO-220 package allowing low-cost assembly without external insulators
• Glass-passivated chip construction providing a rugged barrier against junction contamination
• High surge capability supporting up to 100 A peak one-cycle forward surge current

Applications

• AC switching and phase control applications requiring noise immunity
• Speed controls and temperature modulation systems
• Lighting controls where high voltage isolation is required

Procurement Notes

Verify the specific part number S4008FS21 against official Littelfuse documentation to confirm the isolated TO-220 configuration and 400 V rating. Ensure that the gate trigger current requirements align with the specified 200 µA maximum. Confirm compliance with RoHS standards and check for any custom design variations if standard parameters do not meet application needs.

Selection Notes

Select this component when an electrically isolated SCR is required for circuits operating up to 400 V with an 8 A load. The 200 µA gate sensitivity allows for direct interfacing with logic-level drivers in some scenarios. Consider the thermal resistance characteristics and derating curves for case temperatures above 25 °C to ensure reliable operation within the -40 °C to +110 °C range.

Part Context

This device belongs to the Teccor line of sensitive SCRs, which complements Littelfuse's power SCR portfolio. The series offers ratings from 0.8 A to 10 A and voltages from 200 V to 600 V. The S4008FS21 specifically represents the 8 A, 400 V variant within the isolated TO-220 family, distinguished by its 'F' suffix indicating isolation and 'S2' indicating gate sensitivity class.

Replacement Considerations

Publicly confirmed substitute part numbers are not available in the provided datasheet. Designers should consult Littelfuse directly for equivalent devices or custom design variations that match the specific electrical and isolation requirements.