Texas Instruments LM2577T-15/LB03

Overview

LM2577T-15/LB03 from Texas Instruments is a monolithic step-up (boost) switching voltage regulator with fixed 15 V output, integrated 3.0 A NPN switch, 52 kHz oscillator, and current-mode control. It operates from 3.5 V to 40 V input, delivers up to 600 mA load current, and includes undervoltage lockout, thermal shutdown, and current limiting-used in industrial power supplies and battery-powered instrumentation requiring stable mid-rail boost conversion.

For engineers reviewing the LM2577T-15/LB03 datasheet, LM2577T-15/LB03 pinout, LM2577T-15/LB03 application, or LM2577T-15/LB03 equivalent, key selection criteria include input voltage range compatibility, 15 V fixed-output regulation accuracy, TO-220 thermal performance, NPN switch saturation voltage, and soft-start behavior during cold-boot sequences.

Technical Context

The LM2577T-15/LB03 implements current-mode PWM control using an internal error amplifier with 15 V reference, comparator, and 52 kHz oscillator to regulate output by modulating peak inductor current. Its NPN switch operates with 0.5 V typical saturation voltage at 2.0 A and supports flyback and forward topologies beyond basic boost.

Thermal design relies on the TO-220 (T) package's 65°C/W junction-to-ambient thermal resistance; operation requires external diode, inductor, and input/output capacitors per Figure 9 test circuit. The feedback pin is internally connected to the 15 V output for fixed-voltage versions-no external resistor divider needed.

Key Specifications

Pinout & Package

LM2577T-15/LB03 uses a 5-lead TO-220 (T) package (NS package number T05A), with the tab electrically connected to Pin 2 (Ground). Thermal performance assumes ≥1 in² copper area on PCB; θ_JA = 65°C/W, θ_JC = 2°C/W.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LM2577T-12 and LM2577T-ADJ, the LM2577T-15/LB03 offers optimized 15 V regulation without external feedback components, lower design risk for fixed-rail applications, and identical thermal and switching performance-making it ideal when 15 V is the exact target voltage.

Availability

LM2577T-15/LB03 is available at Aetrix Electronics and suitable for industrial power supplies, battery-powered instrumentation, automotive aftermarket electronics, and legacy equipment retrofit requiring stable component supply and long-term manufacturability.

Supply support for LM2577T-15/LB03 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 switching regulator design and manufacturing.

The LM2577 product line was engineered for cost-effective, robust DC-DC boost conversion in industrial, automotive, and instrumentation applications-emphasizing simplicity, thermal resilience, and minimal external component count.

FAQ

What is the maximum input voltage rating for LM2577T-15/LB03?

The LM2577T-15/LB03 has an absolute maximum input supply voltage of 45 V, with recommended operating range from 3.5 V to 40 V. Exceeding 40 V risks violating the device's safe operating area, especially under transient conditions-designers should verify input surge margins using the 65 V switch voltage rating and external clamping if needed. The LM2577T-15/LB03 remains fully functional within its 40 V upper limit.

Does LM2577T-15/LB03 require external feedback resistors?

No, the LM2577T-15/LB03 is a fixed-output variant: its feedback pin is internally connected to generate precisely 15 V, eliminating the need for external resistors. This simplifies layout, improves regulation accuracy, and removes resistor tolerance and temperature drift variables. Other variants like LM2577T-ADJ do require external resistors, but LM2577T-15/LB03 operates out-of-the-box with only input/output capacitors, inductor, and diode.

What thermal considerations apply to LM2577T-15/LB03 in TO-220 package?

The LM2577T-15/LB03 in TO-220 (T) package has θ_JA = 65°C/W with standard PCB layout (≈1 in² copper). To maintain junction temperature ≤125°C, average power dissipation must stay below ~1.1 W at 25°C ambient. Adequate copper pour under the tab, optional heatsinking, and airflow are critical at >400 mA loads. Thermal derating curves in the datasheet confirm operation up to 125°C junction temperature.

Can LM2577T-15/LB03 be used in flyback or forward converter topologies?

Yes, the LM2577T-15/LB03 supports flyback and forward converter configurations per the datasheet Application Hints. Its integrated NPN switch, current-sense capability, and 65 V standoff make it suitable for isolated designs-though the fixed 15 V feedback connection limits use to non-isolated or opto-coupled feedback variants. For true isolated flyback, the adjustable version (LM2577T-ADJ) is typically preferred due to external feedback flexibility.

What is the purpose of the Bypass pin (Pin 5) on LM2577T-15/LB03?

Pin 5 (Bypass) connects to ground through a 0.1 μF ceramic capacitor to stabilize the internal oscillator and reduce timing jitter. This capacitor filters noise on the oscillator node and ensures consistent 52 kHz switching frequency. Omitting or misplacing this capacitor causes frequency instability, increased EMI, and potential regulation errors. The LM2577T-15/LB03 requires this capacitor for reliable operation-no alternative configuration is supported.