STMicroelectronics LD1117S33TR

Overview

LD1117S33TR from STMicroelectronics is a fixed-output 3.3 V low-dropout linear voltage regulator delivering up to 800 mA output current with 1.1 V typical dropout at 800 mA, ±1 % output voltage tolerance at 25 °C, and 75 dB supply voltage rejection at 120 Hz - used for powering microcontroller I/O rails, FPGA auxiliary supplies, and industrial sensor interfaces.

For engineers reviewing the LD1117S33TR datasheet, LD1117S33TR pinout, LD1117S33TR application, or LD1117S33TR equivalent, this page delivers verified package mapping (SOT-223), thermal resistance (R_thJA = 110 °C/W), minimum stability capacitor (10 µF), adjustable version compatibility (V_REF = 1.25 V), and fixed-voltage alternatives across the LD1117 family.

Technical Context

The LD1117S33TR employs an NPN pass transistor architecture to minimize quiescent current consumption in load-dependent operation, unlike PNP-based regulators where bias current flows independently of load. Its internal bandgap reference and trimming circuitry enable ±1 % initial accuracy at 25 °C and 0.5 % temperature stability over –40 to +125 °C.

Stability is achieved with only a 10 µF ceramic or tantalum output capacitor, eliminating need for ESR-tuned electrolytics. The device integrates thermal shutdown and current limiting, with junction-to-ambient thermal resistance of 110 °C/W in SOT-223, enabling reliable operation at full 800 mA load under moderate airflow or PCB copper area.

Key Specifications

Pinout & Package

SOT-223 package with exposed thermal pad connected internally to V_OUT; 3-pin configuration optimized for surface-mount thermal performance and board space efficiency.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LD1117S33TR, LD1117S33CTR offers superior thermal handling in SO-8 but demands layout redesign, while AMS1117-3.3 sacrifices accuracy, dropout, and temperature range for cost - making LD1117S33TR optimal for industrial and automotive designs requiring guaranteed 3.3 V ±1 % across full temperature range.

Availability

LD1117S33TR is available at Aetrix Electronics and suitable for industrial automation controllers, automotive body electronics, and medical sensor modules requiring stable component supply with long-term lifecycle assurance.

Supply support for LD1117S33TR 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, specializing in power management, microcontrollers, and analog ICs for industrial, automotive, and embedded markets.

The LD1117 series was designed as a cost-effective, thermally robust LDO family targeting high-volume applications needing precise fixed-voltage regulation with minimal external components - particularly in space-constrained SMT designs.

FAQ

What is the minimum input voltage required for stable 3.3 V output at 800 mA?

The LD1117S33TR requires a minimum input voltage of 4.4 V to maintain regulation at 800 mA load, based on its 1.1 V typical dropout voltage. At 100 mA load, input can be as low as 3.4 V. Operation below dropout causes output to track input minus saturation voltage, compromising regulation.

Can LD1117S33TR be used with ceramic output capacitors?

Yes - the LD1117S33TR is stable with 10 µF ceramic capacitors (X5R/X7R) having ESR ≥ 0.1 Ω. Unlike older LDOs, it does not require high-ESR electrolytic or tantalum capacitors, enabling smaller footprints and improved reliability in temperature-cycling environments.

How does the SOT-223 thermal performance compare to DPAK for full-load operation?

In SOT-223, R_thJA is 110 °C/W versus 100 °C/W for DPAK (TO-252). At 800 mA and 1.1 V dropout (0.88 W dissipation), SOT-223 junction temperature rises ~97 °C above ambient - requiring ≥2 cm² of 2-oz copper. DPAK reduces this by ~9 °C, offering margin for sealed enclosures.

Is there a lead-free and RoHS-compliant version of LD1117S33TR?

Yes - LD1117S33TR is manufactured in full compliance with RoHS Directive 2011/65/EU and REACH Regulation (EC) No. 1907/2006. The device uses matte tin lead finish and halogen-free molding compound, with full material declarations available in ST's official compliance documentation.