STMicroelectronics LD1085D2M33R

Overview

LD1085D2M33R from STMicroelectronics is a fixed-output 3.3 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 sensor signal chains where input-to-output headroom is constrained.

For engineers reviewing the LD1085D2M33R datasheet, LD1085D2M33R pinout, LD1085D2M33R application, or LD1085D2M33R 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 trade-offs.

Technical Context

The LD1085D2M33R uses an NPN-based pass transistor architecture that routes quiescent current into the load-unlike PNP regulators-improving efficiency and reducing wasted bias current. Its reference voltage is trimmed on-chip to 1.25 V with ±1% accuracy, enabling tight output regulation without external feedback components.

Dropout voltage remains stable across temperature (–40 °C to +125 °C) and load (0–3 A), with typical 1.3 V at 3 A and <1.5 V maximum. Internal protection includes thermal shutdown and current limiting, with short-circuit current scaling inversely with dropout voltage-ensuring safe fault behavior under varying input conditions.

Key Specifications

Pinout & Package

D²PAK (TO-263) thermally enhanced surface-mount package with exposed drain pad for PCB heat sinking; compatible with standard reflow profiles and industrial assembly lines.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LM3940IT-3.3/NOPB and TLV1117-33CDR, the LD1085D2M33R uniquely combines 3 A capability, D²PAK thermal performance, and 1.3 V dropout in a fixed 3.3 V variant-making it the only viable choice for high-current industrial and networking applications requiring surface-mount reliability and minimal input headroom.

Availability

LD1085D2M33R is available at Aetrix Electronics and suitable for industrial automation, networking infrastructure, and medical diagnostic equipment requiring stable component supply, long-term lifecycle assurance, and consistent parametric performance across production batches.

Supply support for LD1085D2M33R 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 microcontrollers, power management ICs, sensors, and analog devices for industrial, automotive, and consumer markets.

The LD1085 series belongs to ST's high-current linear regulator product line, engineered specifically for applications demanding robust thermal performance, tight output tolerance, and compatibility with legacy 3-terminal regulator footprints in industrial power systems.

FAQ

What is the minimum input voltage required for LD1085D2M33R to maintain regulation at 3 A?

The minimum input voltage is 4.6 V: 3.3 V output plus 1.3 V typical dropout. At 3 A load and 25 °C, regulation is guaranteed down to 4.6 V input; at higher temperatures or worst-case 1.5 V dropout, 4.8 V is recommended for margin. Input below 4.6 V causes output collapse.

Can LD1085D2M33R be used without an input capacitor?

No. A minimum 10 µF input capacitor is required for stability and transient suppression. Without it, the regulator may oscillate or fail to reject line noise-especially during fast input voltage changes. Ceramic or tantalum types are acceptable; place within 5 mm of the IN and GND pins.

Is the D²PAK package of LD1085D2M33R lead-free and RoHS-compliant?

Yes. The LD1085D2M33R is manufactured in ST's ECOPACK®-compliant D²PAK package, meeting RoHS Directive 2011/65/EU and REACH SVHC requirements. Lead-free soldering is supported per JEDEC J-STD-020 moisture sensitivity level 3 (MSL3) handling guidelines.

Does LD1085D2M33R require an external resistor divider for output voltage setting?

No. LD1085D2M33R is a fixed-output variant-its 3.3 V regulation is achieved internally via laser-trimmed resistors. Unlike the adjustable LD1085 (ADJ version), it has no adjust pin and requires no external feedback network, simplifying layout and reducing BOM count.