STMicroelectronics LD1117AS25TR

Overview

LD1117AS25TR from STMicroelectronics is a fixed-output 2.5 V low-dropout linear voltage regulator delivering up to 1 A output current with 1.15 V typical dropout at full load and ±2% output voltage tolerance at 25 °C. It uses an NPN pass transistor, requires only a 10 µF output capacitor for stability, and operates across 0–125 °C junction temperature - deployed in embedded power rails for microcontrollers and sensors.

For engineers reviewing the LD1117AS25TR datasheet, LD1117AS25TR pinout, LD1117AS25TR application, or LD1117AS25TR equivalent, key selection criteria include dropout voltage at 1 A, quiescent current under no-load, thermal resistance (R_thJA = 110 °C/W in SOT-223), supply voltage rejection (80 dB typ.), and compatibility with standard 2.5 V logic and analog subsystems.

Technical Context

The LD1117AS25TR implements a monolithic NPN-based LDO architecture with internal current limiting and thermal shutdown. Its reference voltage is trimmed to achieve ±2% accuracy at 25 °C and maintains ≤0.5% temperature-induced drift over 0–125 °C.

It achieves high PSRR (80 dB typ. at 120 Hz) via internal compensation and stable regulation with minimal external components: only one 10 µF ceramic or electrolytic output capacitor is required. Quiescent current remains tightly controlled at 5 mA typ. (≤10 mA max) across input voltages up to 10 V.

Key Specifications

Pinout & Package

LD1117AS25TR is supplied in SOT-223 package (ECOPACK® compliant), with exposed thermal pad electrically connected to V_OUT. The package enables PCB-level heat spreading and supports >1 A operation with moderate copper area.

Key Features

Applications

Equivalent & Alternatives

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

Compared with TLV1117-25CDR and MCP1702T-2502E/MB, the LD1117AS25TR uniquely balances 1 A capability, 1.15 V dropout, and SOT-223 thermal performance - making it optimal for cost-sensitive industrial and embedded systems requiring robust 2.5 V regulation without over-engineering.

Availability

LD1117AS25TR is available at Aetrix Electronics and suitable for industrial sensor nodes, USB-hosted microcontroller systems, IoT edge devices, and FPGA I/O bank regulation requiring stable component supply and long-term manufacturability.

Supply support for LD1117AS25TR 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 was developed as a cost-optimized, high-reliability LDO family targeting embedded power management in space- and thermal-constrained applications - emphasizing simplicity, stability, and wide operating temperature support.

FAQ

What is the minimum input voltage required for stable 2.5 V output at 1 A load?

The LD1117AS25TR requires VIN ≥ VO + VDROPOUT = 2.5 V + 1.15 V = 3.65 V minimum at 1 A and 25 °C. At higher temperatures or worst-case tolerance, design for ≥3.8 V to ensure margin. Input below this threshold causes dropout and unregulated output.

Can LD1117AS25TR replace adjustable LD1117ASTR in a 2.5 V design?

No - LD1117AS25TR is a fixed 2.5 V variant with internal feedback; LD1117ASTR is adjustable (VREF = 1.25 V) and requires external resistors. They share pinout and thermal characteristics but differ in internal topology and cannot be interchanged without circuit redesign.

Is a bypass capacitor required on the ADJ pin? What about the 2.5 V version?

The ADJ pin exists only on adjustable versions (e.g., LD1117ASTR). LD1117AS25TR has no ADJ pin - it is a 3-pin fixed-output device (IN, OUT, GND). No bypass capacitor is needed or applicable; only the 10 µF output capacitor is mandatory.

Does LD1117AS25TR support ceramic output capacitors?

Yes - the LD1117AS25TR is stable with ceramic, tantalum, or aluminum electrolytic capacitors ≥10 µF and ESR ≤ 1 Ω. Ceramic capacitors are fully compatible and recommended for low-profile, high-reliability layouts due to their longevity and low ESL.