STMicroelectronics LD1085V

Overview

LD1085V from STMicroelectronics is a 3 A low-dropout positive voltage regulator in fixed 5 V output configuration, designed for high-current linear regulation in space-constrained industrial power supplies. It delivers ±1% output tolerance at 25 °C, maintains 1.3 V typical dropout at full 3 A load, operates across –40 °C to +125 °C, and requires only a 10 µF output capacitor for stability - enabling compact, thermally robust 5 V rail generation in motor drives and PLC I/O modules.

For engineers reviewing the LD1085V datasheet, LD1085V pinout, LD1085V application, or LD1085V equivalent, this page provides verified technical context, real-world design meaning of key specs, validated pin functions, application-specific implementation value, and two confirmed alternative parts with documented functional and thermal trade-offs.

Technical Context

The LD1085V uses an NPN-based pass transistor architecture that routes quiescent current into the load rather than wasting it as bias current - directly improving efficiency over legacy PNP regulators. Its internal reference is trimmed to ±1% accuracy at 25 °C and stabilized across temperature via on-chip compensation.

Thermal protection is implemented via junction-temperature sensing with automatic foldback current limiting, and electrical safety is enforced by internal short-circuit current limiting that scales inversely with dropout voltage (e.g., 3.2–4.5 A at 5 V dropout, 0.2–0.5 A at 25 V dropout).

Key Specifications

Pinout & Package

LD1085V is supplied in TO-220 package (3-lead, vertical mounting), with exposed tab electrically connected to the output pin for direct heatsink coupling and low thermal resistance (R_thJC = 3 °C/W).

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 and TLV1117-50, the LD1085V uniquely sustains 3 A at 125 °C junction while delivering tighter voltage accuracy and integrated thermal foldback - making it the sole viable option for high-reliability industrial 5 V rails demanding full-load operation across extended temperature ranges.

Availability

LD1085V is available at Aetrix Electronics and suitable for industrial motor drives, programmable logic controllers, and test & measurement equipment requiring stable component supply with guaranteed long-term manufacturability and consistent parametric performance.

Supply support for LD1085V 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 LD1085V belongs to ST's high-current linear regulator product line, engineered specifically for industrial power conversion where reliability, thermal resilience, and precise voltage regulation supersede switching efficiency.

FAQ

What is the minimum input voltage required for LD1085V to regulate 5 V at 3 A?

The LD1085V requires a minimum input voltage of 6.6 V to maintain 5 V output at full 3 A load, based on its guaranteed 1.5 V maximum dropout voltage. Below this threshold, the device enters dropout mode and output voltage drops linearly with input - verified in Table 6 of the official datasheet under VI = 6.6 to 30 V conditions.

Can LD1085V replace LM317 in existing designs?

Yes - the LD1085V is pin-to-pin compatible with LM317 in TO-220 packages and shares identical IN-OUT-GND pinout. However, it delivers fixed 5 V output instead of adjustable, so replacement requires confirming the target application uses 5 V and removing external feedback resistors. Dropout and thermal performance are significantly improved.

Does LD1085V require an input capacitor?

While not strictly mandatory for stability, ST recommends a minimum 10 µF aluminum or tantalum capacitor at the input pin to suppress high-frequency noise and prevent oscillation during transient load steps. This is especially critical when the input source has >100 mΩ impedance or is fed from a switching converter.

How does LD1085V handle short-circuit conditions?

LD1085V limits short-circuit current based on dropout voltage: 3.2–4.5 A when VI − VO = 5 V, but only 0.2–0.5 A when VI − VO = 25 V. This adaptive current limiting prevents destructive power dissipation during high-voltage shorts and is implemented via internal thermal sensing and foldback circuitry.