Texas Instruments LM2671N-12

Overview

LM2671N-12 from National Semiconductor is a monolithic 500mA step-down (buck) DC-DC voltage regulator in an 8-pin DIP package, delivering a fixed 12V output with ±1.5% tolerance over line and load, 94% efficiency at 24V_IN/500mA, and 260 kHz fixed-frequency switching. It integrates a 0.25Ω DMOS power switch, soft-start, TTL-compatible shutdown, and thermal/current protection - designed for industrial power rails and pre-regulation of linear supplies.

For engineers reviewing the LM2671N-12 datasheet, LM2671N-12 pinout, LM2671N-12 application, or LM2671N-12 equivalent, key selection criteria include input voltage range (8–40V), guaranteed 500mA output current, DIP-8 thermal resistance (95°C/W), and compatibility with standard off-the-shelf inductors and Schottky catch diodes.

Technical Context

The LM2671N-12 implements a current-mode buck topology with internal frequency compensation (U.S. Pat. Nos. 5,382,918 and 5,514,947), enabling stable operation with minimal external components. Its 260 kHz oscillator allows use of compact filter inductors (e.g., 47 μH for 24V_IN/12V_OUT) while maintaining high efficiency (>90%) without heatsinking beyond PCB copper traces.

It features TTL-level ON/OFF control (1.4V threshold, 50 μA standby current), programmable soft-start via external capacitor, and synchronization capability up to 400 kHz. Protection includes cycle-by-cycle current limiting (0.62–1.2 A) and thermal shutdown, ensuring robust fault handling in unregulated input environments.

Key Specifications

Pinout & Package

LM2671N-12 uses an 8-pin dual in-line package (DIP) with through-hole mounting and 0.3-inch lead spacing. Thermal performance relies on PCB copper area adjacent to pins 1 (GND), 2 (VIN), and 7 (SW).

Key Features

Applications

Equivalent & Alternatives

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

Compared with LM2576-12 and TPS5430-12, the LM2671N-12 uniquely balances DIP-8 through-hole compatibility, built-in soft-start/synchronization, and 500 mA capability - making it ideal for industrial upgrades, test equipment, and automotive body modules where layout simplicity and proven reliability outweigh raw current or frequency specs.

Availability

LM2671N-12 is available at Aetrix Electronics and suitable for industrial power supplies, automotive body control units, and legacy system voltage translation requiring stable component supply, long-lifecycle support, and through-hole manufacturability.

Supply support for LM2671N-12 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

National Semiconductor was a U.S.-based semiconductor company specializing in analog and power management ICs, acquired by Texas Instruments in 2011; its SIMPLE SWITCHER® portfolio remains widely deployed in industrial and automotive systems.

The LM2671 series was designed as a family of easy-to-use, high-efficiency buck regulators targeting cost-sensitive, medium-power applications where minimal external components and proven reliability were critical - especially in industrial control, instrumentation, and automotive subsystems.

FAQ

What is the maximum input voltage rating for the LM2671N-12?

The absolute maximum input voltage for the LM2671N-12 is 45 V, but the recommended operating range is 8 V to 40 V. Exceeding 40 V risks violating safe operating area limits even if below 45 V, particularly under transient conditions. The LM2671N-12 datasheet specifies guaranteed performance only within 8–40 V, and thermal stress increases significantly above 36 V at full load.

Does the LM2671N-12 require an external feedback resistor network?

No - the LM2671N-12 is a fixed-output variant with internal feedback divider set for 12 V; the FB pin is not connected internally and must remain unconnected or grounded per National Semiconductor's design guidelines. Using external resistors would disrupt regulation and is incompatible with the LM2671N-12's architecture.

Can the LM2671N-12 be synchronized to an external clock?

Yes - the LM2671N-12 supports frequency synchronization via its SYNC pin (Pin 3). Applying a 400 kHz square wave with ≥3 V_PP and 50% duty cycle synchronizes the internal oscillator, enabling coordinated switching in multi-rail systems to reduce beat-frequency noise. This feature is fully functional on the LM2671N-12 without modification.

What is the thermal resistance (θ_JA) of the LM2671N-12 package?

The LM2671N-12 in its 8-pin DIP package has a junction-to-ambient thermal resistance (θ_JA) of 95°C/W, measured with approximately 1 in² of copper surrounding the leads. This value assumes standard FR-4 PCB construction; adding thermal vias or increasing copper area lowers θ_JA, directly improving sustained 500 mA output capability at elevated ambient temperatures.

Is the LM2671N-12 RoHS compliant?

The LM2671N-12 was originally released in April 2007, prior to full RoHS enforcement for legacy DIP packages. While National Semiconductor offered RoHS-compliant variants (e.g., LM2671MX-12 in SO-8), the N-suffix DIP version is not RoHS-compliant due to leaded solder finish and Pb-containing die attach. For new designs requiring RoHS, the LM2671MX-12 or LM2671LD-12 should be selected instead of the LM2671N-12.