Texas Instruments LM2587T-12/NOPB

Overview

LM2587T-12/NOPB from Texas Instruments is a monolithic 5-A step-up (boost) and flyback switching regulator IC with fixed 12-V output, 4-V to 40-V input range, 100-kHz fixed-frequency oscillator, NPN internal switch rated for 65-V standoff and 5-A peak current, and ±4% system output voltage tolerance over line and load. It enables compact, low-component-count DC/DC conversion in industrial power supplies and battery-powered systems.

For engineers reviewing the LM2587T-12/NOPB datasheet, LM2587T-12/NOPB pinout, LM2587T-12/NOPB application, or LM2587T-12/NOPB equivalent, key selection considerations include its fixed 12-V output configuration, TO-220-5 package thermal performance (R_θJA = 65°C/W), current-mode control architecture, internal soft-start, and undervoltage lockout at 3.3 V.

Technical Context

The LM2587T-12/NOPB implements current-mode PWM control with a 100-kHz fixed-frequency oscillator, using an internal NPN transistor as the primary power switch. Feedback is taken from the output via a resistive divider into the FB pin, compared against a 12-V reference (V_REF = 12.0 V, ±2% typical over temperature).

Protection includes cycle-by-cycle current limiting (ICL = 6.5 A typ), thermal shutdown (T_J(MAX) = 150°C), and undervoltage lockout (V_UV = 3.30 V, ±0.35 V). The error amplifier features transconductance of 0.328 mmho and output swing from 0.25 V to 2.8 V.

Key Specifications

Pinout & Package

LM2587T-12/NOPB is housed in a 5-pin TO-220 (NDH) package with bent staggered leads, 14.986 mm × 10.16 mm body size, and electrically isolated tab connected to Pin 2 (Ground). Thermal performance assumes vertical mounting with ½-inch leads soldered to PCB copper area.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LM2587T-ADJ/NOPB, the LM2587T-12/NOPB eliminates feedback resistor tolerance errors and improves output accuracy; versus LM2577T-12/NOPB, it delivers 67% higher switch current and 100% higher frequency, enabling smaller magnetics and better transient response at full load.

Availability

LM2587T-12/NOPB is available at Aetrix Electronics and suitable for industrial power supplies, battery-powered instrumentation, and automotive aftermarket lighting requiring stable component supply, long-term lifecycle support, and traceable sourcing.

Supply support for LM2587T-12/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 company headquartered in Dallas, Texas, designing and manufacturing analog and embedded processing solutions for industrial, automotive, and personal electronics markets.

The LM2587 series was developed specifically for cost-sensitive, medium-power flyback, boost, and forward converter applications where minimal external components, integrated protection, and fixed-output simplicity are prioritized over programmability.

FAQ

What is the maximum output current achievable with LM2587T-12/NOPB in boost configuration?

The LM2587T-12/NOPB does not internally limit output current in boost mode - only switch current is limited (6.5 A typical). Output current depends on input voltage, duty cycle, and external components. At VIN = 10 V, typical continuous output is ~1.2 A; at VIN = 24 V, it reaches ~0.5 A. External current limiting (e.g., sense resistor + comparator) is required to protect the switch above 5 A peak.

Can LM2587T-12/NOPB be used in flyback topology with multiple outputs?

Yes - the LM2587T-12/NOPB is explicitly designed for multi-output flyback applications. TI's datasheet provides six reference designs (Figures 22–27), including dual- and triple-output configurations using coupled windings and post-regulation. Output cross-regulation relies on transformer turns ratios and winding coupling; tighter regulation requires post-DC/DC converters on auxiliary rails.

What thermal derating applies to LM2587T-12/NOPB in TO-220 package without heatsink?

With R_θJA = 65°C/W and T_J(MAX) = 150°C, maximum allowable power dissipation is (150 − T_A) / 65 W. At T_A = 50°C, PD_MAX ≈ 1.54 W. Since P_D ≈ (V_IN − V_OUT) × I_OUT × (1 − η)⁻¹, continuous 1-A output at 10-V input requires forced air or heatsink; 500-mA load is sustainable at 50°C ambient with PCB copper area.

Does LM2587T-12/NOPB require an external diode in boost configuration?

Yes - LM2587T-12/NOPB requires an external Schottky or ultrafast recovery diode (e.g., 1N5822, MBR20100CT) between the Switch (Pin 5) and output capacitor. The diode must withstand ≥65-V reverse voltage and conduct peak output current (≥1.5× I_OUT). No internal diode is integrated; omission causes catastrophic failure during switch-off transitions.

How does the internal 12-V reference in LM2587T-12/NOPB differ from the adjustable version's 1.23-V reference?

The LM2587T-12/NOPB uses a trimmed, laser-trimmed 12-V bandgap reference directly tied to the FB pin - no external divider needed. In contrast, the LM2587T-ADJ/NOPB provides a 1.23-V reference (±1.5 mV line regulation) requiring external R1/R2 to set V_OUT. The fixed 12-V version achieves ±4% total system tolerance; the adjustable version's accuracy depends on resistor tolerance and layout parasitics.