Texas Instruments LM3411AM5-5.0/NOPB

Overview

LM3411AM5-5.0/NOPB from Texas Instruments is a precision 5-V fixed-output shunt regulator with ±0.5% initial tolerance (A-grade), designed specifically to drive optocouplers in isolated DC-DC feedback loops. It features an open-emitter NPN output capable of 15 mA sink current, internal bandgap reference with curvature correction, and externally accessible COMP pin for loop compensation. Used in flyback converters delivering 5 V at up to 1.5 A.

For engineers reviewing the LM3411AM5-5.0/NOPB datasheet, LM3411AM5-5.0/NOPB pinout, LM3411AM5-5.0/NOPB application, or LM3411AM5-5.0/NOPB equivalent, key selection criteria include regulation accuracy over –40°C to +125°C, low quiescent current (110 μA typ), output saturation voltage (1.2 V max at 15 mA), transconductance (3.3 mA/mV typ), and SOT-23-5 package compatibility with space-constrained power supply designs.

Technical Context

The LM3411AM5-5.0/NOPB implements a precision shunt regulation architecture centered on an internally compensated op-amp and trimmed bandgap reference. Its +IN pin senses regulated output voltage, while the COMP pin provides direct access to the amplifier's inverting input for external frequency compensation-critical for stabilizing isolated flyback control loops.

This device operates as a two-terminal shunt element in feedback paths: when +IN exceeds 5.0 V, the OUT pin sinks current into an optocoupler LED to adjust PWM duty cycle. The internal 94 kΩ feedback resistor (R_f) sets the 5-V regulation point, and its temperature coefficient is characterized to ensure <±1% total error across –40°C to +125°C.

Key Specifications

Pinout & Package

LM3411AM5-5.0/NOPB is housed in a 5-pin SOT-23 (DBV) package measuring 2.90 mm × 1.60 mm, optimized for high-density PCB layouts in isolated power supplies.

Key Features

Applications

Equivalent & Alternatives

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

Compared with TL431ACDR and LM4040C50IDBZR, LM3411AM5-5.0/NOPB uniquely integrates precision 5-V reference, op-amp, and optocoupler-driver transistor in one SOT-23-5 package-with dedicated COMP pin for robust loop stabilization in isolated switching regulators.

Availability

LM3411AM5-5.0/NOPB is available at Aetrix Electronics and suitable for isolated flyback converters, precision buck regulators, negative-input power supplies, and high-accuracy LDO systems requiring stable component supply and long-term manufacturability.

Supply support for LM3411AM5-5.0/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 specializing in analog, embedded processing, and power management ICs, with leadership in high-reliability power conversion solutions.

The LM3411AM5-5.0/NOPB belongs to TI's precision shunt regulator product line, engineered specifically for secondary-side feedback in isolated DC-DC converters-emphasizing accuracy, thermal stability, and seamless optocoupler interfacing.

FAQ

What is the primary function of the LM3411AM5-5.0/NOPB in a power supply design?

The LM3411AM5-5.0/NOPB functions as a precision 5-V shunt regulator and optocoupler driver in the secondary-side feedback path of isolated DC-DC converters. It senses output voltage at the +IN pin, compares it to its internal 5-V reference, and sinks current from the OUT pin to modulate the optocoupler LED-thereby adjusting the primary-side PWM controller to maintain tight output regulation. This role is explicitly defined in TI's datasheet Section 3 (Description) and Figure 19 (Typical Application Schematic).

Does the LM3411AM5-5.0/NOPB require external resistors to set its output voltage?

No, the LM3411AM5-5.0/NOPB does not require external resistors to set its output voltage. It is a fixed 5-V device with internal trimmed feedback resistors (94 kΩ nominal) that establish the regulation point. As stated in Section 8.3 ("Feature Description") and Electrical Characteristics Table 6.6, the device regulates +IN to exactly 5.0 V ±0.5% at 25°C-eliminating the need for external divider networks or trimming components.

How is the COMP pin used in LM3411AM5-5.0/NOPB circuits?

The COMP pin on the LM3411AM5-5.0/NOPB is the inverting input of the internal operational amplifier and is used for external loop compensation. Per Section 9.2.1.2.1 and Figure 19, a capacitor (e.g., 10 nF) is typically connected between COMP and OUT to set the dominant pole and ensure stable closed-loop response. This direct access enables precise Bode plot tuning-critical for maintaining ≥45° phase margin in high-bandwidth isolated flyback converters.

What is the maximum output current the LM3411AM5-5.0/NOPB can sink, and what limits it?

The LM3411AM5-5.0/NOPB can sink up to 15 mA continuously at the OUT pin, as specified in Section 6.3 ("Recommended Operating Conditions") and confirmed in Absolute Maximum Ratings (20 mA). This limit is constrained by junction temperature rise: at 25°C ambient, the 178.6 °C/W R_θJA and 150°C max T_J allow ~69 mW dissipation, corresponding to 15 mA × 1.2 V V_SAT. Exceeding 15 mA risks thermal shutdown or parametric shift, especially above 85°C ambient.

Can the LM3411AM5-5.0/NOPB be used in negative-output power supplies?

Yes, the LM3411AM5-5.0/NOPB supports negative-output configurations. Section 9.2.5 ("Negative Input, Negative or Positive Output Flyback Regulator") details its use with –20 V to –10 V inputs delivering –5 V at 1 A. In this setup, the device references its GND pin to the negative output rail, and the +IN pin senses voltage relative to that rail-enabling accurate regulation regardless of output polarity. The SOT-23 package and internal architecture make it suitable for both positive and negative secondary-side implementations.