Texas Instruments LM2574N-15/NOPB

Overview

LM2574N-15/NOPB from Texas Instruments is a monolithic 0.5A step-down (buck) switching voltage regulator in an 8-pin PDIP package, delivering a fixed 15V output with ±4% tolerance over line and load, 52 kHz fixed-frequency operation, and integrated thermal shutdown and cycle-by-cycle current limiting. It replaces linear regulators in industrial power supplies requiring efficient 15V rail generation from up to 40V input.

For engineers reviewing the LM2574N-15/NOPB datasheet, LM2574N-15/NOPB pinout, LM2574N-15/NOPB application, or LM2574N-15/NOPB equivalent, key selection criteria include its 40V max input, 0.5A guaranteed output, 72–88% efficiency across input ranges, TTL-compatible shutdown, and requirement for only four external components - making it suitable for cost-sensitive, thermally constrained DC/DC designs.

Technical Context

The LM2574N-15/NOPB integrates a PWM controller, power switch, oscillator, error amplifier, and protection circuitry into a single silicon die. Its fixed-frequency 52 kHz architecture enables predictable EMI filtering and simplifies inductor selection using standardized off-the-shelf parts.

It operates in continuous conduction mode at full load, with internal current limiting set at 0.7–1.8 A peak and thermal shutdown activating at 150°C junction temperature. The feedback loop uses a precision 1.23V reference (not present in fixed-output variants), but the 15V version internally routes this reference to generate regulation without external resistors.

Key Specifications

Pinout & Package

LM2574N-15/NOPB is housed in an 8-pin plastic dual in-line package (PDIP), NS package code N08A, with Pin 1 marked by dot or notch. Thermal performance relies on soldering Pin 3 (Ground) and Pin 8 (Input) to large copper areas; Pin 5 (Feedback) is not connected in fixed-output versions.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar step-down regulator applications.

Compared with LM2574HVN-15, the LM2574N-15/NOPB trades input voltage headroom for lower cost and identical thermal behavior at 40V max; versus LM2596-15, it offers proven reliability and simpler magnetics at the expense of current capability and efficiency - making it ideal for established 0.5A industrial designs.

Availability

LM2574N-15/NOPB is available at Aetrix Electronics and suitable for industrial automation, embedded control, and test equipment requiring stable component supply, long-term obsolescence management, and traceable sourcing.

Supply support for LM2574N-15/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 acquired National Semiconductor in 2011 and maintains full technical support and manufacturing continuity for the SIMPLE SWITCHER™ product line.

The LM2574N-15/NOPB belongs to TI's SIMPLE SWITCHER™ family of integrated buck regulators, designed specifically for ease-of-use, minimal external component count, and robust operation in industrial and embedded power applications.

FAQ

What is the maximum input voltage rating for LM2574N-15/NOPB?

The LM2574N-15/NOPB has a maximum input voltage rating of 40 V, with absolute maximum limit at 45 V. Operation above 40 V violates the specified operating range and risks instability or premature failure. For 48V or higher input systems, the LM2574HVN-15 variant (60 V max) is the appropriate alternative. Always verify input transient margins against this 40 V limit when designing with LM2574N-15/NOPB.

Does LM2574N-15/NOPB require external feedback resistors?

No, the LM2574N-15/NOPB does not require external feedback resistors. As a fixed-output variant, its 15 V regulation is implemented internally; Pin 5 (Feedback) is unconnected per the datasheet. External resistors are only needed for the adjustable version (LM2574N-ADJ). Using resistors with LM2574N-15/NOPB will not alter output voltage and may interfere with internal regulation.

What is the typical efficiency of LM2574N-15/NOPB at full load?

The LM2574N-15/NOPB achieves 88% typical efficiency at VIN = 18 V, VOUT = 15 V, and IOUT = 0.5 A. Efficiency varies with input voltage - e.g., 72% at VIN = 12 V - due to fixed switching losses and duty-cycle effects. These values are measured under standard test conditions with recommended external components and 4 in² PCB copper area; actual efficiency depends on layout, component ESR, and ambient temperature.

Can LM2574N-15/NOPB be used in discontinuous conduction mode?

Yes, the LM2574N-15/NOPB operates reliably in both continuous and discontinuous conduction modes. At light loads (<~50 mA), inductor current naturally drops to zero, entering discontinuous mode - a normal, documented behavior that maintains regulation without instability. The datasheet provides design guidance for both modes, and no external changes are needed to support either.

What package type is LM2574N-15/NOPB supplied in?

The LM2574N-15/NOPB is supplied in an 8-pin plastic dual in-line package (PDIP), National Semiconductor package code N08A. It is not available in surface-mount packages; the M-suffix variants (e.g., LM2574M-15) use a 14-lead wide SOIC. This through-hole package supports manual assembly, prototyping, and high-reliability industrial applications where mechanical robustness is prioritized.