STMicroelectronics LD1117AS12TR

Overview

LD1117AS12TR from STMicroelectronics is a fixed-output 1.2 V low-dropout linear voltage regulator in SOT-223 package, delivering up to 1 A output current with 1.15 V typical dropout at full load, ±2% output voltage tolerance at 25 °C, and 80 dB supply voltage rejection. It serves as a primary post-regulator in embedded power rails for microcontrollers and sensors requiring stable, low-noise 1.2 V supply.

For engineers reviewing the LD1117AS12TR datasheet, LD1117AS12TR pinout, LD1117AS12TR application, or LD1117AS12TR equivalent, key selection criteria include dropout voltage at 1 A, thermal resistance (R_thJA = 110 °C/W), minimum stability capacitance (10 µF), quiescent current (5 mA typ.), and compatibility with 0–125 °C industrial temperature operation.

Technical Context

The LD1117AS12TR uses an NPN pass transistor architecture enabling low dropout while maintaining internal current and thermal limiting. Its reference voltage is trimmed to achieve ±2% output accuracy at 25 °C, with 0.5% temperature stability across 0–125 °C junction range.

Stability requires only a 10 µF output capacitor; input and output capacitors are both specified at 10 µF in test conditions. The device operates with input voltages from 2.75 V to 10 V and supports load currents from 0 to 1 A without external compensation.

Key Specifications

Pinout & Package

SOT-223 package with exposed thermal pad connected internally to V_OUT; footprint optimized for PCB heat spreading via copper pour under tab.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LD1117DT12TR, the LD1117AS12TR trades thermal performance for compact surface-mount integration; versus TLV1117-12CDCYR, it offers higher output current and better thermal robustness at the cost of slightly looser initial tolerance.

Availability

LD1117AS12TR is available at Aetrix Electronics and suitable for industrial control systems, medical sensor interfaces, and networking equipment requiring stable component supply with full production lifecycle support.

Supply support for LD1117AS12TR 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.

The LD1117A series targets cost-sensitive, high-reliability linear regulation needs in industrial and embedded systems where simplicity, thermal resilience, and long-term supply stability are prioritized over ultra-low IQ or ultra-high PSRR.

FAQ

What is the minimum input voltage required for stable 1.2 V output at 1 A load?

The LD1117AS12TR requires VIN ≥ VO + VD = 1.2 V + 1.30 V (max dropout @ 1 A) = 2.5 V. However, ST specifies 2.75 V as the minimum guaranteed operating input voltage across temperature and process variation, ensuring regulation integrity under worst-case conditions including thermal drift and line/load transients.

Can the LD1117AS12TR be used with ceramic output capacitors?

Yes - ST's datasheet confirms stability with 10 µF ceramic capacitors having ESR ≥ 10 mΩ. Unlike older LDOs, the LD1117A does not require minimum ESR; its internal compensation is compatible with low-ESR ceramics, enabling smaller footprint and improved transient response compared to electrolytic alternatives.

Is thermal shutdown reversible without power cycle?

Yes - the LD1117AS12TR features automatic thermal foldback and hysteresis-based shutdown. Once junction temperature drops ~15 °C below the 165 °C trip point (typically to ~150 °C), the device resumes normal regulation without requiring input power removal or reset signaling.

Does the SOT-223 package require solder paste stencil aperture adjustments for thermal pad reliability?

Yes - ST recommends a 70–80% solder paste coverage ratio on the exposed thermal pad (pin 2/tab) with 4–6 vias (0.3 mm diameter) thermally connecting to inner ground planes. This prevents voiding and ensures R_thJC ≤ 15 °C/W, critical for sustaining 1 A continuous output in ambient >60 °C.