Texas Instruments LM2576T-ADJ/NOPB

Overview

LM2576T-ADJ/NOPB from Texas Instruments is a monolithic 3-A non-synchronous step-down DC-DC switching regulator in TO-220-5 package, delivering adjustable output voltage from 1.23 V to 37 V with ±4% regulation accuracy over line and load, 52-kHz fixed-frequency operation, and integrated thermal shutdown and cycle-by-cycle current limiting - used in industrial power supplies and embedded motor drives.

For engineers reviewing the LM2576T-ADJ/NOPB datasheet, LM2576T-ADJ/NOPB pinout, LM2576T-ADJ/NOPB application, or LM2576T-ADJ/NOPB equivalent, key selection considerations include input voltage range (up to 40 V), feedback reference voltage (1.23 V), ON/OFF logic polarity (low-enable), saturation voltage (1.8 V max at 3 A), and thermal resistance (32.4°C/W junction-to-ambient in KC package).

Technical Context

The LM2576T-ADJ/NOPB implements a fixed-frequency buck topology with internal 52-kHz oscillator, error amplifier referencing 1.23 V at the FB pin, and a single NPN power switch rated for 3-A DC output. It operates in continuous conduction mode under full load and transitions to discontinuous mode at light loads without instability.

Control logic includes TTL-compatible ON/OFF pin (active-low enable), cycle-by-cycle peak current limiting (ICL = 4.2–6.9 A), and thermal shutdown activation above 150°C junction temperature. Feedback is resistive-divider based, requiring no compensation components beyond standard input/output capacitors and inductor.

Key Specifications

Pinout & Package

LM2576T-ADJ/NOPB uses the KC (TO-220-5) package with 10.16 mm × 8.51 mm body size and integral heat tab electrically connected to GND. The tab must be soldered to a large copper pour for thermal management.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LM2576HV-ADJ/NOPB, the LM2576T-ADJ/NOPB trades input voltage headroom for cost and thermal optimization at ≤40 V inputs; versus LMR51430RGER, it sacrifices efficiency and integration for proven reliability, minimal BOM count, and zero-compensation design.

Availability

LM2576T-ADJ/NOPB is available at Aetrix Electronics and suitable for industrial motor drives, embedded system auxiliary supplies, test equipment DC modules, and appliance mainboard power requiring stable component supply across long-lifecycle production programs.

Supply support for LM2576T-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 is a global semiconductor leader specializing in analog, embedded processing, and power management ICs, with decades of expertise in rugged, high-reliability power conversion solutions.

The LM2576 series was designed as a drop-in, high-efficiency replacement for three-terminal linear regulators in industrial, automotive, and consumer power systems - emphasizing simplicity, fault resilience, and thermal robustness.

FAQ

What is the maximum input voltage rating for LM2576T-ADJ/NOPB?

The absolute maximum input voltage for LM2576T-ADJ/NOPB is 45 V, but the recommended operating maximum is 40 V per TI's datasheet. Exceeding 40 V risks violating safe operating area limits and may trigger thermal shutdown or reduce long-term reliability. For 48-V systems, LM2576HV-ADJ/NOPB (60-V rated) is the appropriate variant. Always verify input transient margins in your application before finalizing the design using LM2576T-ADJ/NOPB.

How do I configure LM2576T-ADJ/NOPB for a specific output voltage?

LM2576T-ADJ/NOPB uses a resistive voltage divider on the FEEDBACK pin to set output voltage: VOUT = 1.23 V × (1 + R2/R1), where R1 connects from FB to GND and R2 from VOUT to FB. For example, 5 V requires R2 ≈ 3.1 kΩ with R1 = 1 kΩ. The feedback pin draws only 50 nA, so resistor values can be high (e.g., 10 kΩ–100 kΩ) to minimize divider current. Ensure both resistors are 1% tolerance metal film for ±4% output accuracy. This configuration applies exclusively to LM2576T-ADJ/NOPB - fixed-output versions omit the divider.

Does LM2576T-ADJ/NOPB require an external catch diode?

Yes, LM2576T-ADJ/NOPB requires an external Schottky catch diode (e.g., 1N5822 or SB560) connected between the OUTPUT pin and GND. The internal switch is a single NPN transistor, so the diode provides the return current path during switch-off time. Diode selection must meet 3-A average current, ≥60-V PIV, and low forward voltage (≤0.55 V) to maintain efficiency. Omitting the diode will cause catastrophic failure. This requirement is inherent to LM2576T-ADJ/NOPB's non-synchronous architecture and differs from synchronous converters like LMR51430.

What thermal management is required for LM2576T-ADJ/NOPB at full 3-A load?

At 3-A output with 12-V input and 5-V output, LM2576T-ADJ/NOPB dissipates ~3.6 W. With RθJA = 32.4°C/W (KC package), junction temperature rise is ~117°C above ambient - requiring a heatsink or ≥1 in² copper pour to keep TJ ≤ 125°C. Mounting the tab directly to a 2-oz copper plane with multiple thermal vias reduces θJA to ~25°C/W. Without thermal relief, the device enters thermal shutdown within seconds. Thermal design is mandatory for sustained 3-A operation and is a core constraint in LM2576T-ADJ/NOPB implementation.

Can LM2576T-ADJ/NOPB be synchronized to an external clock?

No, LM2576T-ADJ/NOPB cannot be synchronized to an external clock. Its 52-kHz oscillator is fully internal and fixed-frequency; there is no SYNC pin or frequency-adjust capability. This simplifies design but means EMI filtering must target 52 kHz and harmonics. For applications requiring clock synchronization (e.g., multi-rail systems), alternatives like LM5115 or TPS54302 provide external sync inputs. The lack of synchronization is a defined architectural limitation of LM2576T-ADJ/NOPB and applies across all variants in the family.