STMicroelectronics LD1084D2M90R

Overview

LD1084D2M90R from STMicroelectronics is a 5A low-dropout positive voltage regulator with fixed 9.0V output, TO-220-compatible D2PAK package, ±1% output tolerance at 25°C, 1.3V typical dropout at 5A, and operation from −40°C to +125°C junction temperature - used in industrial power supplies requiring stable high-current regulation under tight input headroom.

For engineers reviewing the LD1084D2M90R datasheet, LD1084D2M90R pinout, LD1084D2M90R application, or LD1084D2M90R equivalent, key selection factors include guaranteed 5A output current, thermal-limited internal protection, minimal external capacitance (10µF), quiescent current flowing into load for improved efficiency, and compatibility with legacy 3-terminal adjustable regulator footprints.

Technical Context

The LD1084D2M90R implements a PNP-based LDO architecture with on-chip trimming for ±1% initial output accuracy and integrated thermal shutdown and current limiting. Its reference voltage is internally generated and stabilized across temperature, enabling tight line and load regulation (≤20mV over 0–5A).

Unlike traditional PNP regulators, its quiescent current flows entirely into the load rather than being wasted as bias current, improving conversion efficiency especially at light loads. Dropout voltage remains ≤1.5V up to full 5A output, with thermal resistance junction-to-case of 3°C/W in D2PAK package.

Key Specifications

Pinout & Package

D2PAK package (TO-263 variant): thermally enhanced surface-mount outline with exposed metal pad for PCB heat transfer; compatible footprint with TO-220 but optimized for automated assembly and higher power density.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LM2940CT-9.0/NOPB and LT1963AET-9, the LD1084D2M90R uniquely delivers 5A output with sub-1.5V dropout and load-connected quiescent current - making it the only option among the three capable of sustaining high-current industrial loads under tight input margins while maximizing light-load efficiency.

Availability

LD1084D2M90R is available at Aetrix Electronics and suitable for industrial power supplies, SCSI-2 termination circuits, telecom line cards, and motor drive control logic requiring stable component supply with long-term lifecycle support.

Supply support for LD1084D2M90R 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 power management applications.

The LD1084 series belongs to ST's high-current linear regulator product line, engineered specifically for industrial and telecom systems demanding robust thermal performance, wide temperature operation, and pin-compatible upgrades to legacy regulators.

FAQ

What is the minimum input voltage required for LD1084D2M90R to maintain regulation at 5A?

The LD1084D2M90R requires a minimum input voltage of 10.3V to sustain 9.0V output at 5A, based on its maximum dropout voltage of 1.5V. At lighter loads, dropout decreases - e.g., ~0.8V at 2A - allowing operation from as low as 9.8V. Input must remain ≥4.5V for functional operation per absolute maximum ratings.

Can LD1084D2M90R replace an LM317 in an existing design?

Yes - the LD1084D2M90R uses the same 3-pin TO-220/D2PAK pinout (IN-OUT-GND) as the LM317, enabling direct mechanical replacement. However, it is a fixed 9V device, so it replaces LM317 only in designs where output is hardwired to 9V and no adjustment is needed. No external resistors are required.

Is a heatsink mandatory for continuous 5A operation?

A heatsink is strongly recommended for continuous 5A operation. With R_thJC = 3°C/W and max T_J = 125°C, even at 25°C ambient, power dissipation of ~6.5W (5A × 1.3V dropout) would raise junction temperature to ~145°C without heatsinking. A low-thermal-resistance heatsink (e.g., ≤10°C/W) is required to stay within safe limits.

Does LD1084D2M90R require an input capacitor?

An input capacitor is not strictly required for stability but is highly recommended: a 10µF–47µF low-ESR electrolytic or tantalum capacitor placed near the IN pin suppresses high-frequency noise and prevents oscillation caused by source impedance. ST's typical application circuits specify 10µF input capacitance for optimal transient response and EMI reduction.