STMicroelectronics LD1085DT15R

Overview

LD1085DT15R from STMicroelectronics is a fixed-output 1.5 V, 3 A low-dropout linear voltage regulator in TO-220FP package. It delivers stable output with ±1% tolerance at 25 °C, 1.3 V typical dropout at full load, and operates across –40 °C to +125 °C junction temperature. Used in industrial power rails requiring high-current, low-noise, and thermally robust regulation.

For engineers reviewing the LD1085DT15R datasheet, LD1085DT15R pinout, LD1085DT15R application, or LD1085DT15R equivalent, key selection criteria include dropout voltage at 3 A, thermal resistance (R_thJC = 5 °C/W), output tolerance over temperature, quiescent current behavior under load, and compatibility with minimal 10 µF output capacitance for stability.

Technical Context

The LD1085DT15R implements an NPN-based LDO architecture with internal bandgap reference (1.25 V) and error amplifier, enabling high-accuracy output regulation without external feedback resistors. Its adjustable variant uses the ADJ pin to set VO = V_REF(1 + R1/R2), but this fixed 1.5 V version integrates trimming for ±1% initial accuracy and ±2% over full temperature range.

Thermal protection and current limiting are fully integrated, with short-circuit current scaling inversely with dropout voltage (e.g., 5.5–6.5 A at 5 V dropout, 0.5–0.7 A at 25 V dropout). Quiescent current flows into the load-not wasted as bias-improving efficiency versus PNP regulators.

Key Specifications

Pinout & Package

LD1085DT15R is housed in a TO-220FP (Full-Pak) package: insulated case, vertical mounting, 3-pin through-hole configuration with integral heatsink tab. The plastic body provides electrical isolation between case and pin 2 (GND), simplifying thermal design.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LD1085V15, the LD1085DT15R trades 2 °C/W higher junction-to-case thermal resistance for electrical isolation-critical in floating-ground or safety-isolated systems. Versus TLV1117-15CDCY, it delivers 3.75× more current, superior thermal robustness, and integrated protection-making it the sole viable choice for 3 A industrial 1.5 V rails.

Availability

LD1085DT15R is available at Aetrix Electronics and suitable for industrial automation, automotive body electronics, and medical imaging equipment requiring stable component supply, long-lifecycle assurance, and traceable sourcing.

Supply support for LD1085DT15R 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 analog, MCU, power, and MEMS products for industrial, automotive, and consumer markets.

The LD1085 series belongs to ST's high-current linear regulator product line, engineered specifically for industrial power management applications demanding reliability, thermal resilience, and precision output regulation under variable load and temperature conditions.

FAQ

What is the minimum input voltage required for LD1085DT15R to regulate 1.5 V at 3 A?

The minimum input voltage is determined by dropout: VI(min) = VO + V_d = 1.5 V + 1.5 V (max spec) = 3.0 V. At 3 A load and 25 °C, typical dropout is 1.3 V, so 2.8 V input sustains regulation. Input must remain ≥2.85 V per datasheet absolute min rating to avoid undefined behavior.

Can LD1085DT15R be used with ceramic output capacitors?

Yes-ST specifies stability with ≥10 µF ceramic or tantalum output capacitors. Unlike older LDOs, it does not require ESR-based damping; low-ESR ceramics are fully supported and recommended for reduced size and improved transient response.

Does LD1085DT15R have reverse polarity or reverse current protection?

No-the device lacks integrated reverse-battery or reverse-current blocking. If input can go below output (e.g., during hot-swap or backup battery switchover), an external Schottky diode from IN to OUT is required to prevent backfeed and potential damage.

How does quiescent current behave under no-load and full-load conditions?

Quiescent current remains 5–10 mA across all loads (0–3 A) and input voltages ≤30 V. Crucially, this current flows *into* the load-not to ground-so total supply current equals I_OUT + I_Q, improving system efficiency versus traditional PNP LDOs where I_Q is load-independent and wasted.