Texas Instruments LM3411M5-3.3/NOPB

Overview

LM3411M5-3.3/NOPB from Texas Instruments is a precision 3.3 V shunt regulator IC designed specifically to drive optocouplers in isolated DC-DC switching regulator feedback loops. It features ±0.5% initial regulation tolerance (A-grade), 15 mA output current capability, 5-pin SOT-23 package, and internal bandgap reference with curvature correction for stable operation from –40°C to +125°C.

For engineers reviewing the LM3411M5-3.3/NOPB datasheet, LM3411M5-3.3/NOPB pinout, LM3411M5-3.3/NOPB application, or LM3411M5-3.3/NOPB equivalent, this page delivers verified functional role, real-world compensation interface details, confirmed thermal metrics, exact voltage gain and transconductance values, and validated alternative options for isolated power supply design.

Technical Context

The LM3411M5-3.3/NOPB integrates a trimmed bandgap reference, internally compensated op-amp, and open-emitter NPN output transistor - all optimized for closed-loop voltage regulation via external optocoupler feedback. Its COMP pin provides direct access to the op-amp's inverting input for loop stability tuning using external RC networks.

It operates as a two-terminal shunt regulator where regulation occurs between +IN and GND, while OUT sources current into the optocoupler LED. The device maintains regulation across 20 μA–15 mA load range with <1.3 V saturation voltage at full load and 50 μV_RMS output noise (10 Hz–10 kHz).

Key Specifications

Pinout & Package

LM3411M5-3.3/NOPB is housed in a 5-pin SOT-23 (DBV) package measuring 2.90 mm × 1.60 mm, optimized for space-constrained isolated power designs.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar shunt regulator applications.

Compared with TL431ACDR and LM4040C33IDBZR, LM3411M5-3.3/NOPB uniquely combines fixed 3.3 V precision, optocoupler-ready NPN output, and accessible COMP pin - enabling single-chip isolated feedback without external gain stages or trimming components.

Availability

LM3411M5-3.3/NOPB is available at Aetrix Electronics and suitable for isolated DC-DC converters, precision LDO references, negative-output flyback supplies, and high-accuracy monitoring circuits requiring stable component supply and long-term manufacturability.

Supply support for LM3411M5-3.3/NOPB includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Texas Instruments is a global semiconductor company delivering analog and embedded processing solutions, with leadership in power management, signal chain, and high-reliability ICs.

The LM3411M5-3.3/NOPB belongs to TI's precision shunt regulator product line, engineered specifically for optocoupler-based feedback in isolated switching power supplies - prioritizing regulation accuracy, thermal stability, and ease of loop compensation.

FAQ

What is the primary function of the LM3411M5-3.3/NOPB in a power supply design?

The LM3411M5-3.3/NOPB serves as a precision secondary-side shunt regulator that senses output voltage and drives an optocoupler to close the feedback loop in isolated DC-DC converters. Its 3.3 V ±0.5% reference, open-emitter NPN output, and accessible COMP pin make LM3411M5-3.3/NOPB ideal for achieving tight regulation without external trimming components or complex compensation networks.

How does the COMP pin on the LM3411M5-3.3/NOPB affect system stability?

The COMP pin exposes the inverting input of the internal error amplifier, allowing designers to add external RC compensation to tailor loop bandwidth and phase margin. For example, a capacitor from COMP to OUT sets dominant pole frequency; mismatched Rf tolerance (39–65 kΩ) means worst-case phase margin occurs at minimum Rf, so LM3411M5-3.3/NOPB designs must verify stability across full Rf range per datasheet Table 6.5.

Can the LM3411M5-3.3/NOPB be used in negative-output power supplies?

Yes - LM3411M5-3.3/NOPB can regulate negative outputs by referencing its +IN and GND pins to the positive side of a reversed-winding secondary. Figure 26 in the official datasheet shows a –20 V to –10 V input, –5 V/1 A flyback using LM3411M5-3.3/NOPB to provide level-shifted feedback. The device itself remains ground-referenced; polarity inversion is handled by transformer topology, not LM3411M5-3.3/NOPB configuration.

What is the maximum allowable input voltage for the LM3411M5-3.3/NOPB?

The absolute maximum input voltage (applied to +IN pin) for LM3411M5-3.3/NOPB is 20 V, as specified in Section 6.1 of the datasheet. Exceeding this risks permanent damage. In normal operation, +IN is held near 3.3 V by regulation; transient overvoltage events (e.g., during startup or fault) must be clamped externally if system conditions could push +IN above 20 V.

Does the LM3411M5-3.3/NOPB require external resistors for basic operation?

No - LM3411M5-3.3/NOPB integrates precision feedback resistors (39–65 kΩ) and requires no external resistors to achieve 3.3 V regulation. External components are only needed for loop compensation (RC network on COMP pin) and current limiting (series resistor on OUT if driving high-CTR optocouplers beyond 15 mA). This eliminates tolerance stack-up and reduces BOM count versus adjustable references like TL431.