LM3411M5-3.3/NOPB

Overview

The LM3411M5-3.3/NOPB is a precision secondary regulator and driver manufactured by Texas Instruments, designed specifically for driving optoisolators to provide feedback in isolated power supply applications. This fixed-voltage shunt regulator operates at a nominal output of 3.3V with an initial accuracy of ±1%. It features a low operating supply current of 85 µA and supports a maximum cathode current of 15 mA. The device is housed in a compact SOT-23-5 surface-mount package, ensuring efficient integration into space-constrained designs while maintaining stable regulation performance.

Feature Summary

• Designed specifically for driving optoisolators to provide feedback in isolated power supplies
• Fixed voltage output with high initial accuracy for precise regulation
• Low power consumption suitable for energy-efficient applications

Applications

• Flyback converter secondary side regulation
• Isolated DC-DC converter feedback loops
• Switching power supply control circuits

Procurement Notes

Verify the complete part number including the suffix /NOPB to ensure lead-free compliance and specific package variant. Confirm the fixed 3.3V output requirement matches the design specifications. Check the datasheet for thermal management requirements associated with the SOT-23-5 package under maximum load conditions. Ensure compatibility with the intended optoisolator drive current limits.

Selection Notes

Select this component when a dedicated secondary-side regulator for optocoupler driving is required rather than a general-purpose shunt reference. The fixed 3.3V output eliminates the need for external resistor dividers, simplifying the circuit design. Consider the low quiescent current for battery-operated or efficiency-critical systems. Verify that the 15 mA cathode current capability meets the peak drive requirements of the connected optoisolator.

Part Context

This device belongs to the LM3411 family of precision secondary regulators. Unlike standard voltage references such as the TL431 which require external components for programming, the LM3411 integrates the necessary biasing and drive circuitry specifically for optoisolator interfaces. It serves as a drop-in replacement for discrete transistor-based feedback solutions, offering improved stability and reduced component count in isolated power conversion topologies.

Replacement Considerations

Direct substitutes include other LM3411 variants with different fixed voltages (e.g., LM3411M5-5.0) if the system requires 5V instead of 3.3V. General-purpose shunt regulators like the TL431 can functionally replace it but require additional external resistors and may not offer the same optimized drive characteristics for optoisolators.