4N31SM

Overview

The 4N31SM is a single-channel optoisolator manufactured by Isocom Components 2004 LTD. It features an infrared LED input paired with a Darlington transistor output that includes a base terminal for enhanced switching control. The device provides high electrical isolation of 5300Vrms between input and output circuits. It is housed in a surface-mount package designed for compact circuit board layouts, suitable for applications requiring reliable signal transmission across isolated boundaries.

Feature Summary

• Integrates an infrared emitting diode with a Darlington phototransistor output structure
• Includes a dedicated base pin to facilitate faster turn-off times and improved switching performance
• Provides robust galvanic isolation between input and output sections via optical coupling

Applications

• Industrial control systems requiring signal isolation
• Computer peripheral interface circuits
• Solid-state relay driver applications
• Microcontroller interfacing for noise immunity

Procurement Notes

Verify component authenticity through authorized distributors or direct manufacturer channels. Confirm the specific suffix designation matches project requirements. Check current availability status as this part may be subject to discontinuation notices. Ensure proper handling procedures are followed during storage and assembly to maintain device integrity.

Selection Notes

Select this component when a Darlington output configuration is required for higher current gain compared to standard phototransistors. The integrated base connection allows for external biasing to optimize switching speed. Consider the surface-mount form factor for automated assembly processes and space-constrained designs.

Part Context

This device belongs to the family of general-purpose optocouplers designed for digital signal isolation. It serves as a replacement for legacy through-hole components in modern surface-mount designs. The Darlington architecture offers superior sensitivity for low-level input signals while maintaining high output drive capability within isolated environments.

Replacement Considerations

Direct substitutes include the 4N31S from onsemi. Verify pinout compatibility and thermal characteristics before substitution. Ensure the replacement maintains the same isolation voltage rating and package dimensions for mechanical fit.