STMicroelectronics LD1085DT18R

Overview

LD1085DT18R from STMicroelectronics is a fixed-output 1.8 V, 3 A low-dropout linear voltage regulator in D²PAK package, featuring ±1% output tolerance at 25 °C, 1.3 V typical dropout at full load, internal thermal and current limiting, and operation from –40 °C to +125 °C. It delivers stable power to microcontroller cores, FPGA I/O banks, and industrial PLC logic rails requiring tight regulation under high-current transient loads.

For engineers reviewing the LD1085DT18R datasheet, LD1085DT18R pinout, LD1085DT18R application, or LD1085DT18R equivalent, this page provides verified electrical parameters, thermal resistance data (R_thJC = 3 °C/W), stability requirements (10 µF min. output capacitor), and real-world use context for embedded power design validation.

Technical Context

The LD1085DT18R uses an NPN-based pass transistor architecture that routes quiescent current into the load-unlike PNP regulators-improving efficiency at light loads. Its reference voltage is trimmed to 1.25 V with ±1.0% accuracy, enabling precise 1.8 V output via internal resistor network.

It integrates thermal shutdown triggered at junction temperature ≥165 °C and foldback current limiting that reduces short-circuit current as dropout decreases. The device maintains stability with ceramic or tantalum output capacitors ≥10 µF and requires no external compensation.

Key Specifications

Pinout & Package

D²PAK (TO-263) thermally enhanced surface-mount package with exposed metal tab for PCB heatsinking; 3-pin configuration: Input (Pin 1), Ground (Pin 2), Output (Pin 3).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar fixed-output LDO applications.

Compared with TLV1117-18CDR and TPS7A4701RGWR, the LD1085DT18R uniquely combines 3 A output, D²PAK thermal performance, and fixed 1.8 V accuracy-making it irreplaceable for high-current industrial logic rails where both power density and regulation stability are non-negotiable.

Availability

LD1085DT18R is available at Aetrix Electronics and suitable for industrial automation controllers, automotive body electronics, medical sensor hubs, and networking infrastructure requiring stable component supply across extended temperature ranges and multi-year production cycles.

Supply support for LD1085DT18R 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

STMicroelectronics is a global semiconductor leader headquartered in Geneva, Switzerland, designing and manufacturing silicon solutions for automotive, industrial, and consumer markets since 1987.

The LD1085 series belongs to ST's high-current linear regulator product line, engineered specifically for industrial and automotive subsystems demanding robust thermal behavior, tight DC accuracy, and long-term reliability without switching noise.

FAQ

What is the minimum input voltage required for stable 1.8 V output at 3 A?

The LD1085DT18R requires a minimum input voltage of 3.4 V to maintain regulation at 3 A load, based on its 1.3 V typical dropout voltage. At 3.1 V input, output collapses to ~1.8 V − (3.1 V − 1.8 V) = 0.5 V due to dropout limitation. Designers must ensure ≥3.4 V under worst-case line and load conditions.

Can the LD1085DT18R be used with ceramic output capacitors?

Yes-ST specifies compatibility with ceramic, tantalum, or aluminum electrolytic capacitors ≥10 µF. Unlike older LDOs, it does not require ESR for stability. Ceramic capacitors are preferred for low-profile designs and improved transient response, provided they meet the minimum capacitance and voltage rating (≥6.3 V).

Does the D²PAK package require solder paste stencil aperture adjustments for thermal pad reflow?

Yes-the exposed metal tab in the D²PAK package must be soldered to a large PCB copper area using a thermal relief pattern. ST recommends a 70–80% solder paste coverage ratio on the tab pad and 4–6 thermal vias (0.3 mm diameter, filled or capped) connecting to inner ground planes to achieve R_thJA ≤62.5 °C/W.

How does the LD1085DT18R handle short-circuit conditions?

Under short-circuit, the LD1085DT18R activates foldback current limiting: output current drops from 3.2 A (at 5 V dropout) to 0.2 A (at 25 V dropout), reducing power dissipation and preventing thermal runaway. Simultaneous thermal shutdown engages if junction temperature exceeds 165 °C, latching off until cool-down.