STMicroelectronics LD1085D2M50

Overview

LD1085D2M50 from STMicroelectronics is a fixed-output 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 junction temperature. It delivers stable power to microcontroller core supplies, industrial PLC I/O modules, and embedded sensor signal chains requiring tight regulation under variable load.

For engineers reviewing the LD1085D2M50 datasheet, LD1085D2M50 pinout, LD1085D2M50 application, or LD1085D2M50 equivalent, this page provides verified technical context, real-world design meaning of key specs, validated pin functions, application-specific implementation guidance, and confirmed alternative parts with documented functional differences.

Technical Context

The LD1085D2M50 implements a PNP-based LDO architecture with an internal 1.25 V reference and feedback-controlled pass transistor, enabling fixed 5 V output without external resistors. Its quiescent current flows into the load-not wasted as bias-improving efficiency over legacy PNP regulators.

Dropout voltage remains ≤1.5 V across –40 °C to +125 °C and full 3 A load, while supply voltage rejection exceeds 60 dB at 120 Hz with 25 µF output capacitance. Stability requires only a 10 µF ceramic or tantalum output capacitor.

Key Specifications

Pinout & Package

LD1085D2M50 is housed in a surface-mount D²PAK (TO-263) thermally enhanced package with exposed drain pad for PCB heat sinking. Thermal resistance is R_thJC = 3 °C/W and R_thJA = 62.5 °C/W on 2-layer 1-in² copper.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LM2940CT-5.0/NOPB and TLV1117-50, LD1085D2M50 uniquely delivers 3 A at 1.3 V dropout in a thermally optimized D²PAK, making it the sole choice for high-current, high-temperature industrial and automotive LDO applications requiring guaranteed performance across full load and temperature range.

Availability

LD1085D2M50 is available at Aetrix Electronics and suitable for industrial motor control, automotive body electronics, medical monitoring devices, and test equipment requiring stable component supply with full traceability and lifecycle continuity.

Supply support for LD1085D2M50 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 applications demanding robust thermal performance, wide temperature operation, and precise output regulation without external components.

FAQ

What is the minimum input voltage required for LD1085D2M50 to maintain 5 V output at 3 A?

The LD1085D2M50 requires a minimum input voltage of 6.3 V to sustain 5 V output at 3 A load, based on its maximum dropout voltage of 1.5 V. At typical 1.3 V dropout, 6.3 V input ensures margin for line and load regulation. Input below 6.3 V causes output collapse or unregulated behavior.

Can LD1085D2M50 replace an adjustable LM317 in an existing design?

Yes-LD1085D2M50 is pin-compatible with LM317 in TO-220 and D²PAK footprints, but operates as a fixed 5 V device. To replace LM317, remove the adjustment resistor network and connect ADJ pin to GND (if present), then verify thermal design meets 3 A power dissipation requirements using the D²PAK's 3 °C/W junction-to-case resistance.

Is an input capacitor required for stability?

An input capacitor is not mandatory for stability but strongly recommended: a 10 µF aluminum or tantalum capacitor placed within 1 cm of the input pin reduces high-frequency noise and improves transient response. The regulator remains stable with only the required 10 µF output capacitor, per ST's application schematic and layout guidelines.

Does LD1085D2M50 support reverse-polarity protection?

No-LD1085D2M50 lacks built-in reverse-polarity protection. If input polarity reversal is possible, an external series Schottky diode (e.g., SB560) must be added between the input source and the regulator's VIN pin to prevent catastrophic failure, as reverse voltage beyond –0.3 V damages the internal structure.