Texas Instruments LMS1585ACSX-1.5/NOPB

Overview

LMS1585ACSX-1.5/NOPB from Texas Instruments is a 1.5V fixed-output, 5A low-dropout linear regulator in DDPAK/TO-263 (KTT) package. It delivers fast transient response, 1.2V typical dropout at 5A, 0.05% load regulation, and operates across 0°C to 125°C. It powers Pentium® and PowerPC® microprocessor core supplies where stable low-voltage bias with high current capability is required.

For engineers reviewing the LMS1585ACSX-1.5/NOPB datasheet, LMS1585ACSX-1.5/NOPB pinout, LMS1585ACSX-1.5/NOPB application, or LMS1585ACSX-1.5/NOPB equivalent, key selection criteria include output voltage accuracy (±1%), thermal shutdown behavior, dropout performance at full load, and compatibility with 10 µF minimum output capacitance for stability.

Technical Context

The LMS1585ACSX-1.5/NOPB integrates a zener-trimmed bandgap reference, internal current limiting (5.0–6.6A), and thermal shutdown circuitry. Its control architecture uses a single-stage pass element with fixed 1.5V output set by on-die resistor network - no external feedback components required.

It features 72 dB ripple rejection at 120 Hz with 25 µF tantalum output capacitor, 0.003%/W thermal regulation, and 120 µA maximum adjust pin current - though unused in this fixed-voltage variant. The device is optimized for low-noise, high-current DC/DC post-regulation in microprocessor power rails.

Key Specifications

Pinout & Package

Package: DDPAK/TO-263 (KTT), 3-pin, surface-mount, thermally enhanced with exposed die pad. Pin 1 = INPUT, Pin 2 = OUTPUT, Pin 3 = GND (tab connected to GND).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar LDO regulator applications.

Compared with LT1585A-1.5#PBF and LMS1585ACT-1.5/NOPB, the LMS1585ACSX-1.5/NOPB offers tighter output tolerance, superior thermal performance in SMT layouts, and active production status - making it optimal for volume-manufactured microprocessor power rails.

Availability

LMS1585ACSX-1.5/NOPB is available at Aetrix Electronics and suitable for Pentium® processor supplies, PowerPC® system rails, and FPGA configuration voltage applications requiring stable component supply, long-term lifecycle assurance, and RoHS-exempt Pb-free compliance.

Supply support for LMS1585ACSX-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-reliability power management solutions since 1930.

The LMS1585A series was developed specifically for high-current, low-dropout regulation in microprocessor and logic supply applications - emphasizing fast transient response, thermal robustness, and compatibility with standard 10 µF output capacitors.

FAQ

What is the minimum input voltage required for LMS1585ACSX-1.5/NOPB to maintain regulation?

The LMS1585ACSX-1.5/NOPB requires a minimum input voltage of 2.7V to sustain 1.5V output at 5A load, based on its 1.2V typical dropout voltage. At lighter loads, input can drop to 2.5V while remaining in regulation. Operation below 2.5V risks dropout and unregulated output - design margin should include worst-case dropout of 1.4V per datasheet limits.

Does LMS1585ACSX-1.5/NOPB require an external capacitor on the ADJ pin?

No - the LMS1585ACSX-1.5/NOPB is a fixed-output variant with internal feedback resistors; the ADJ pin is not brought out and is not accessible. Unlike adjustable versions (e.g., LMS1585ACSX-ADJ/NOPB), this part has no ADJ terminal and does not require external compensation components.

Can LMS1585ACSX-1.5/NOPB be paralleled for higher current output?

No - the LMS1585ACSX-1.5/NOPB is not designed for parallel operation. Its internal current limit and thermal shutdown lack master-slave coordination, and mismatched dropout voltages would cause uneven current sharing. For >5A requirements, use a single higher-current regulator or switch to a multiphase DC/DC solution.

What is the thermal resistance (θJA) of LMS1585ACSX-1.5/NOPB in standard JEDEC 2S2P board layout?

The published θJA for LMS1585ACSX-1.5/NOPB is not specified in the datasheet for JEDEC boards; only junction-to-case (θJC = 0.65°C/W) is guaranteed. Actual θJA depends heavily on PCB copper area, layer count, and thermal vias under the exposed tab. With 4 in² of 2-oz copper and 9 thermal vias, typical θJA is ~35°C/W - sufficient for 5A operation at TA ≤ 65°C.

Is LMS1585ACSX-1.5/NOPB pin-compatible with LMS1585ACS-1.5?

Yes - LMS1585ACSX-1.5/NOPB and LMS1585ACS-1.5 share identical KTT (TO-263) package, 3-pin pinout, and electrical specifications. The "X" suffix denotes tape-and-reel packaging (500 pcs/reel), while non-X variants ship in tubes (45 pcs). Both are RoHS-exempt, Pb-free, and functionally interchangeable in PCB layout.