Texas Instruments LMS1585ACT-1.5/NOPB

Overview

LMS1585ACT-1.5/NOPB from Texas Instruments is a 1.5V fixed-output, 5A low-dropout linear regulator in TO-220 package, featuring 1.2V typical dropout at 5A, 0.05% load regulation, and fast transient response optimized for microprocessor core supplies. It integrates thermal shutdown and current limiting, operates from 0°C to 125°C, and requires only two external capacitors for stable operation.

For engineers reviewing the LMS1585ACT-1.5/NOPB datasheet, LMS1585ACT-1.5/NOPB pinout, LMS1585ACT-1.5/NOPB application, or LMS1585ACT-1.5/NOPB equivalent, key selection considerations include output voltage accuracy (±2%), dropout performance under full load, thermal resistance (2.7°C/W junction-to-case), ripple rejection (60 dB at 120 Hz), and compatibility with standard TO-220 heatsinking solutions.

Technical Context

The LMS1585ACT-1.5/NOPB uses an internal zener-trimmed bandgap reference and NPN pass transistor architecture to deliver precise 1.5V output with minimal input–output differential. Its control loop is optimized for fast load-step response-critical for Pentium® and PowerPC® supply rails where dynamic current demands exceed 3A/µs.

Thermal protection activates at 150°C junction temperature, and current limiting is fixed at 5.0–6.6A. The device draws 7–13 mA quiescent current and maintains regulation down to 0 mA load, eliminating need for minimum load resistors in most applications.

Key Specifications

Pinout & Package

Package: TO-220 (NDE), 3-pin vertical mounting, tab-connected to output (VOUT). Requires mechanical isolation if heatsink is grounded.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar low-dropout linear regulator applications.

Compared with LMS1585ACT-1.5/NOPB, the LMS1585ACS-1.5/NOPB offers superior thermal management in compact designs, while the LMS1587CT-1.5/NOPB provides a cost-efficient 3A alternative with identical mechanical fit-both require validation of thermal design and load profile before substitution.

Availability

LMS1585ACT-1.5/NOPB is available at Aetrix Electronics and suitable for Pentium® processor supplies, PowerPC® I/O rails, and industrial PLC logic supplies requiring stable component supply, long-term manufacturability, and RoHS-compliant packaging.

Supply support for LMS1585ACT-1.5/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 ICs, embedded processors, and high-performance power management solutions since 1930.

The LMS1585A series was developed specifically for high-current, low-voltage microprocessor core and I/O rail regulation-emphasizing fast transient response, thermal robustness, and compatibility with legacy TO-220 heatsink infrastructure.

FAQ

What is the maximum input voltage for the LMS1585ACT-1.5/NOPB?

The absolute maximum input-to-ground voltage for the LMS1585ACT-1.5/NOPB is 13V. However, the recommended operating input range is 3V to 7V to ensure proper regulation and thermal performance. Exceeding 7V significantly increases power dissipation-e.g., at 5A output and 10V input, power loss exceeds 42W, exceeding safe junction temperature limits without aggressive heatsinking.

Does the LMS1585ACT-1.5/NOPB require an external capacitor on the ADJ pin?

No-the LMS1585ACT-1.5/NOPB is a fixed-output variant with internal resistor divider; it has no ADJ pin. Its pinout is strictly INPUT–OUTPUT–GND. Only adjustable versions (e.g., LMS1585ACS-ADJ) expose the ADJ terminal. This simplifies design by eliminating external feedback components and associated layout sensitivity.

Can the LMS1585ACT-1.5/NOPB be used in parallel for higher current?

No-LMS1585ACT-1.5/NOPB is not designed for parallel operation. Its output voltage tolerance (±2%) and load regulation (0.05%) make current sharing unstable without external ballasting resistors or active current-sharing circuitry. TI does not characterize or guarantee performance in parallel configurations; use a single 5A device or select a higher-current regulator instead.

What is the thermal resistance from junction to ambient for the LMS1585ACT-1.5/NOPB?

The datasheet does not specify a fixed junction-to-ambient (θJA) value for LMS1585ACT-1.5/NOPB because it depends entirely on PCB layout and heatsink implementation. The junction-to-case (θJC) is 2.7°C/W. For a standard TO-220 mounted on 1 in² copper with 2 oz Cu and one thermal via, θJA is typically ~35°C/W; with a 10°C/W heatsink, total θJA drops to ~12.7°C/W-supporting ~15W continuous dissipation at 25°C ambient.

Is the LMS1585ACT-1.5/NOPB pin-compatible with Linear Technology LT1585A-1.5?

Yes-the LMS1585ACT-1.5/NOPB is explicitly documented as a direct replacement for LT1585A-1.5, sharing identical pinout (INPUT–OUTPUT–GND), electrical specifications, and TO-220 package outline. Both devices exhibit matched dropout, regulation, and protection behavior, enabling drop-in substitution without PCB modification or firmware changes.