onsemi LM2574N-3.3G

Overview

LM2574N-3.3G from Texas Instruments is a monolithic 0.5-A non-synchronous step-down (buck) DC-DC regulator in PDIP-8 package, delivering a fixed 3.3-V output with ±4% tolerance over line and load, 40-V max input voltage, and 52-kHz fixed-frequency operation. It serves as an efficient replacement for linear regulators in embedded power rails, industrial controllers, and distributed power systems.

For engineers reviewing the LM2574N-3.3G datasheet, pinout, applications, or equivalent options, key selection considerations include its 3.3-V fixed output, thermal shutdown and cycle-by-cycle current limiting, TTL-compatible ON/OFF control, 72% efficiency at 12-V input/0.5-A load, and minimal external component count (4 total).

Technical Context

The LM2574N-3.3G integrates a 0.5-A NPN switch, 1.23-V bandgap reference, error amplifier, 52-kHz oscillator, and PWM comparator in a single PDIP-8 IC. Its non-synchronous architecture uses an external diode for freewheeling, and feedback is internally tied to the output for fixed-voltage versions-eliminating external resistors.

Operation relies on fixed-frequency pulse-width modulation with internal frequency compensation. Shutdown is achieved via TTL-level ON/OFF pin (VIH ≥ 2.2 V), drawing only 50 μA standby current. Protection includes thermal shutdown and peak-current limiting at 0.7–1.6 A.

Key Specifications

Pinout & Package

LM2574N-3.3G is housed in an 8-pin plastic dual in-line package (PDIP) with 0.3-inch body width and through-hole mounting. Thermal performance relies on soldering PWR_GND and SIG_GND pins directly to large copper areas.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LM2574N-3.3G, LM2575N-3.3 offers higher current headroom but demands board revision for pinout change, while MP1584EN-LF-Z delivers superior power density and efficiency at the cost of losing TTL shutdown and increasing design validation effort.

Availability

LM2574N-3.3G is available at Aetrix Electronics and suitable for industrial automation, automotive body electronics, medical sensor hubs, and point-of-sale terminals requiring stable component supply across extended product lifecycles.

Supply support for LM2574N-3.3G 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 headquartered in Dallas, Texas, specializing in analog, embedded processing, and power management technologies with broad industrial and automotive focus.

The LM2574x SIMPLE SWITCHER® series was designed to simplify DC-DC conversion for engineers needing robust, low-component-count buck regulators in cost-sensitive and thermally constrained applications.

FAQ

What is the maximum input voltage rating for LM2574N-3.3G?

The LM2574N-3.3G has a maximum supply voltage rating of 45 V per absolute maximum ratings, with recommended operating input voltage up to 40 V. Exceeding 40 V continuously may reduce reliability or trigger thermal shutdown. The HV variant (LM2574HV) supports up to 60 V, but LM2574N-3.3G is the standard-voltage version and must not be operated beyond 40 V in normal use. Always observe derating guidelines at elevated temperatures.

Does LM2574N-3.3G require external feedback resistors?

No, LM2574N-3.3G does not require external feedback resistors. As a fixed-output variant, its FB pin is internally connected to the OUTPUT pin, establishing the 3.3-V regulation setpoint without external components. This simplifies design, improves accuracy by eliminating resistor tolerance effects, and reduces bill-of-materials count-unlike the adjustable LM2574ADJ, which requires two external resistors to set VOUT.

How does the ON/OFF pin function on LM2574N-3.3G?

The ON/OFF pin on LM2574N-3.3G provides TTL-compatible enable control: pulling it below 1.2 V (typically to GND) activates regulation, while raising it above 2.2 V disables the output and reduces quiescent current to 50 μA typical. The pin draws only 12–30 μA when high, enabling direct interfacing with microcontrollers or logic gates without buffering. Leaving the pin floating is prohibited-it must be actively driven or pulled low via resistor.

What thermal considerations apply to LM2574N-3.3G in PDIP-8 package?

LM2574N-3.3G in PDIP-8 has a junction-to-ambient thermal resistance (RθJA) of 60.4°C/W. At 0.5-A load and 12-V input, power dissipation is ~4.3 W, resulting in ~260°C junction rise above ambient-exceeding the 150°C absolute maximum. Therefore, derating is essential: full 0.5-A output is only sustainable below ~85°C ambient with adequate PCB copper area. Use of thermal vias under PWR_GND/SIG_GND and minimizing trace length to input/output capacitors significantly improves real-world thermal performance.

Can LM2574N-3.3G be used in a positive-to-negative buck-boost configuration?

Yes, LM2574N-3.3G can be configured as a positive-to-negative converter (inverting buck-boost) per TI's application notes, using the OUTPUT pin as the switching node and grounding the FB pin to the negative output rail. However, the fixed 3.3-V feedback reference means the magnitude of the negative output will be approximately –3.3 V, not adjustable. Output current capability is reduced compared to buck mode due to duty-cycle limitations and diode conduction losses, and careful attention to layout and diode selection (fast recovery, low Vf) is required for stable operation.