Texas Instruments LM2574HVN-ADJ/NOPB

Overview

LM2574HVN-ADJ/NOPB from Texas Instruments (formerly National Semiconductor) is a monolithic 0.5A step-down (buck) switching voltage regulator with adjustable output, 52 kHz fixed-frequency oscillator, internal current limiting and thermal shutdown, and 1.23V feedback reference. It operates from 4V to 60V input and delivers up to 37V output (±4% tolerance), requiring only four external components for basic operation. It serves as a high-efficiency replacement for linear regulators in industrial power supplies and embedded DC/DC conversion.

For engineers reviewing the LM2574HVN-ADJ/NOPB datasheet, LM2574HVN-ADJ/NOPB pinout, LM2574HVN-ADJ/NOPB application, or LM2574HVN-ADJ/NOPB equivalent, key selection considerations include its HV input range (up to 60V), adjustable output capability via resistive divider, 52 kHz fixed switching frequency, thermal shutdown behavior, and compatibility with standard off-the-shelf inductors and Schottky catch diodes.

Technical Context

The LM2574HVN-ADJ/NOPB integrates a PWM controller, power switch, oscillator, error amplifier, and current-limit protection in an 8-pin DIP package. Its feedback loop references a precise 1.23V internal bandgap, enabling output programming from 1.23V to 37V using two external resistors. The 52 kHz oscillator drives the internal NPN transistor switch with cycle-by-cycle current limiting and automatic thermal foldback.

It operates in continuous conduction mode by default but transitions to discontinuous mode at light loads. Input voltage rejection and load regulation are maintained across −40°C to +125°C junction temperature, with standby current of 50 µA (typical) when the ON/OFF pin is pulled high.

Key Specifications

Pinout & Package

LM2574HVN-ADJ/NOPB is housed in an 8-pin plastic DIP (NS package N08A) with exposed pad soldered to PCB for thermal transfer. Pin 1 is marked with dot; Pin 5 is internally unconnected but must be soldered to ground plane for optimal thermal performance.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LM2574HVN-ADJ/NOPB, LM2575HVN-ADJ/NOPB offers double the output current in identical packaging, while TPS54202DRCT provides higher integration and frequency at the cost of design complexity and non-drop-in layout compatibility.

Availability

LM2574HVN-ADJ/NOPB is available at Aetrix Electronics and suitable for industrial automation, automotive subsystems, and test equipment requiring stable component supply, long-lifecycle support, and legacy-compatible through-hole packaging.

Supply support for LM2574HVN-ADJ/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 the SIMPLE SWITCHER™ product line as a portfolio of easy-to-use, robust DC/DC converters targeting cost-sensitive and reliability-critical applications.

The LM2574 series was designed specifically for engineers needing simple, proven buck regulator solutions with minimal external components, wide input range, and rugged protection features - especially in industrial and legacy system upgrades.

FAQ

What is the maximum output voltage achievable with LM2574HVN-ADJ/NOPB?

The LM2574HVN-ADJ/NOPB supports an adjustable output voltage range of 1.23V to 37V under normal operating conditions, and up to 57V for the HV version under specified input and load conditions. This is achieved by configuring the external resistor divider between the output and FB pin, referencing the internal 1.23V bandgap. The upper limit is constrained by the breakdown rating of the internal switch and external components-not by the IC's feedback architecture alone.

Does LM2574HVN-ADJ/NOPB require an external diode, and what type is recommended?

Yes, LM2574HVN-ADJ/NOPB requires an external Schottky catch diode connected from the OUT pin to GND. Recommended types include MBR150 (50V, 1A), 11DQ05, or SR105 - all selected for low forward voltage (<0.55V) and fast recovery to minimize conduction loss and switching stress. The diode's reverse voltage rating must exceed 1.25× the maximum input voltage, and its current rating should be ≥1.5× the maximum load current.

Can LM2574HVN-ADJ/NOPB operate with an input voltage below 7V?

Yes, LM2574HVN-ADJ/NOPB has a minimum operating input voltage of 4V, verified across the full temperature range. However, output regulation is only guaranteed when VIN exceeds VOUT by sufficient margin to sustain the required duty cycle - typically VIN ≥ VOUT + 2V for stable operation. At very low input voltages near dropout, efficiency drops and thermal stress increases due to higher switch conduction losses.

How is thermal performance affected by the NC pin (Pin 5) on LM2574HVN-ADJ/NOPB?

Pin 5 on LM2574HVN-ADJ/NOPB has no internal connection but must be soldered to the PCB ground plane to serve as a thermal conduction path. Leaving it unconnected degrades θJA from 72°C/W (with 4 in² copper) to 92°C/W (with 1 in² copper), increasing junction temperature by up to 25°C under full load. National Semiconductor explicitly states this connection is required for best heat transfer in the datasheet.

Is LM2574HVN-ADJ/NOPB compatible with ceramic output capacitors?

LM2574HVN-ADJ/NOPB is optimized for aluminum electrolytic output capacitors (e.g., 220 µF, 25V) due to their ESR characteristics, which aid loop stability. While ceramic capacitors can be used, their near-zero ESR may cause instability or oscillation unless compensated with a series RC network at the COMP pin. The datasheet does not guarantee stable operation with ceramic-only output capacitance without additional external compensation.