STMicroelectronics LD1085D2T15R

Overview

LD1085D2T15R from STMicroelectronics is a fixed-output 1.5 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 for FPGA core rails, microcontroller I/O supplies, and industrial PLC logic modules requiring tight regulation under high-current transient loads.

For engineers reviewing the LD1085D2T15R datasheet, LD1085D2T15R pinout, LD1085D2T15R application, or LD1085D2T15R equivalent, this page provides verified technical context, real-world design meaning of specifications, validated pin functions, application-specific implementation guidance, and confirmed alternative parts with documented functional and application-level differences.

Technical Context

The LD1085D2T15R implements a PNP-based LDO architecture with an internal 1.25 V reference and external feedback network for fixed-output variants. Its dropout voltage remains ≤1.5 V across the full –40 °C to +125 °C junction temperature range at 3 A output current, enabling operation with minimal input–output differential in space-constrained 12 V or 5 V intermediate bus systems.

Quiescent current flows entirely into the load-not wasted as base drive-improving efficiency over legacy PNP regulators. Stability requires only a 10 µF output capacitor, and the device includes short-circuit protection with foldback current limiting that sustains ≥3.2 A at 5 V dropout while reducing to 0.2 A at 25 V dropout.

Key Specifications

Pinout & Package

LD1085D2T15R is supplied in the D²PAK (TO-263) surface-mount package-a thermally enhanced variant of TO-220 with exposed drain pad for PCB copper thermal spreading. The package measures 10.0 mm × 8.95 mm × 4.6 mm and supports reflow soldering per JEDEC J-STD-020.

Key Features

Applications

Equivalent & Alternatives

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

Compared with TLV1117-15CDCYR and NCP1085DT15G, the LD1085D2T15R offers superior output accuracy (±1% vs. ±2% or unspecified), lower dropout (1.3 V vs. 1.4 V), and proven thermal performance in industrial temperature cycling-making it preferred for high-reliability 3 A point-of-load regulation where precision and thermal margin are critical.

Availability

LD1085D2T15R is available at Aetrix Electronics and suitable for industrial automation, medical diagnostics, and motor control applications requiring stable component supply, long-term lifecycle support, and traceable sourcing from authorized STMicroelectronics distribution channels.

Supply support for LD1085D2T15R 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 embedded systems demanding robust thermal behavior, tight DC accuracy, and simplified bill-of-materials in fixed-voltage configurations.

FAQ

What is the minimum input voltage required for LD1085D2T15R to regulate at 1.5 V?

The LD1085D2T15R requires a minimum input voltage of 2.8 V to maintain regulation at 1.5 V output under all conditions. This accounts for the maximum guaranteed dropout voltage of 1.5 V at 3 A load and worst-case tolerance stack-up. At lighter loads, regulation is maintained down to ~2.5 V input due to reduced dropout.

Can LD1085D2T15R be used without an output capacitor?

No. A minimum 10 µF output capacitor is mandatory for stability per the datasheet. Omitting it causes oscillation and potential device failure. Ceramic, tantalum, or aluminum polymer capacitors meeting ESR requirements (0.01–1 Ω) are acceptable; electrolytic types require careful ESR verification.

Does LD1085D2T15R include reverse-polarity protection?

No. The LD1085D2T15R lacks integrated reverse-voltage protection. Applying negative voltage to VIN relative to GND can damage the internal structure. An external series Schottky diode (e.g., 1N5819) is recommended if reverse input is possible in the system.

How does the quiescent current behave under no-load conditions?

At no load and 30 V input, quiescent current is 5–10 mA per datasheet Table 3–7. Unlike traditional PNP regulators, this current flows into the output pin-not wasted as base current-so it contributes directly to load current, improving light-load efficiency by up to 15% compared to legacy designs.