Texas Instruments LM2587T-12

Overview

LM2587T-12 from Texas Instruments is a monolithic 5A flyback/boost regulator IC with fixed 12V output, integrated 5.0A NPN switch rated for 65V standoff, 100 kHz fixed-frequency oscillator, and internal soft-start. It delivers ±4% system output voltage tolerance over line and load, supports input voltages from 4V to 40V, and is used in isolated DC-DC power supplies for industrial control and telecom infrastructure.

For engineers reviewing the LM2587T-12 datasheet, LM2587T-12 pinout, LM2587T-12 application, or LM2587T-12 equivalent, this page provides verified technical context, confirmed pin functions, real-world design meaning of key specs, validated alternative parts, and supply support details for production deployment.

Technical Context

The LM2587T-12 implements current-mode control with cycle-by-cycle current limiting, enabling stable regulation under transient load and line variations. Its error amplifier features 70 V/V voltage gain and 0.328 mmho transconductance, referenced to a 12.0V internal feedback threshold (11.79–12.24V over temperature).

It integrates undervoltage lockout (3.05–3.75V), thermal shutdown, and soft-start via 11.0 μA internal current source. The 100 kHz oscillator drives the NPN switch with up to 98% duty cycle, supporting flyback, boost, and forward topologies without external timing components.

Key Specifications

Pinout & Package

LM2587T-12 is housed in a 5-lead TO-220 (T-package) with bent, staggered leads and electrically isolated tab. Thermal performance depends on PCB copper area: θJA = 65°C/W (minimal copper) or 45°C/W (4 in² copper).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar flyback/boost regulator applications.

Compared with LM2587S-12, the LM2587T-12 offers mechanical heatsink compatibility and electrical isolation, while UC3845N trades integration for configurability-neither is pin-compatible, and both require full schematic and layout revalidation.

Availability

LM2587T-12 is available at Aetrix Electronics and suitable for industrial power supplies, telecom line cards, automotive body control units, and medical sensor modules requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for LM2587T-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

Texas Instruments is a global semiconductor leader specializing in analog and embedded processing technologies, with decades of expertise in power management ICs.

The LM2587 series was designed specifically for cost-sensitive, high-reliability flyback, boost, and forward converter applications-emphasizing minimal external components, robust protection, and production-ready performance.

FAQ

What is the maximum output current supported by the LM2587T-12 in flyback configuration?

The LM2587T-12 supports up to 1.2A output current in flyback topology under specified conditions (VIN = 4–10V, TJ ≤ 125°C), as guaranteed by its electrical characteristics table. This limit arises from internal current limiting and thermal constraints-not the 5A switch rating alone-because output current depends on transformer turns ratio, duty cycle, and efficiency. For LM2587T-12 designs, always verify transformer saturation and thermal rise at full load.

Does the LM2587T-12 require external feedback resistors to set the output voltage?

No, the LM2587T-12 does not require external feedback resistors. It is a fixed-output variant with an internal 12.0V reference connected directly to the feedback pin, eliminating the need for R1/R2 dividers. External resistors are only required for the LM2587-ADJ version. Using resistors with LM2587T-12 would disrupt regulation and is not supported.

Can the LM2587T-12 be used in boost configuration, and what are the key layout considerations?

Yes, the LM2587T-12 supports boost topology per TI's Figure 35 application circuit. Critical layout practices include minimizing high-current loop area (input cap → Pin 1 → Pin 5 → inductor → diode → output cap), placing the 0.1 μF ceramic input capacitor within 5 mm of Pins 1 and 2, and routing the feedback trace away from noisy switch nodes to avoid regulation instability. Inductor selection must match 100 kHz operation and handle ≥5A peak current.

What thermal management is required for continuous operation of the LM2587T-12 at full load?

At full 1.2A output into 12V with 10V input (η ≈ 90%), power dissipation is ~1.3W. With θJA = 65°C/W (minimal copper), junction temperature rise is ~85°C-requiring ambient ≤ 40°C for safe operation. For reliable 24/7 use, mount LM2587T-12 on a 25 mm × 25 mm copper pad (≥1 oz) and add a small aluminum heatsink (≥10 cm²) to keep TJ < 125°C. Derate output current above 60°C ambient.

How does the LM2587T-12 handle short-circuit conditions in boost mode?

In boost configuration, the LM2587T-12 cannot limit output current during a short because energy bypasses the internal switch via the inductor and diode path. The device will enter hiccup or latch-off mode only if junction temperature exceeds 150°C or input voltage drops below UVLO. To protect downstream circuits, external current limiting-such as an input fuse, electronic circuit breaker, or foldback limiter-is mandatory for boost applications using LM2587T-12.