STMicroelectronics LD1117S50TR

Overview

LD1117S50TR from STMicroelectronics is a fixed-output 5.0 V low-dropout linear voltage regulator delivering up to 800 mA, featuring 1.0 V typical dropout at 100 mA, ±1 % output voltage tolerance at 25 °C, and 75 dB supply voltage rejection at 120 Hz - used in embedded power rails for microcontrollers, sensors, and industrial I/O modules.

For engineers reviewing the LD1117S50TR datasheet, LD1117S50TR pinout, LD1117S50TR application, or LD1117S50TR equivalent, this page delivers verified electrical specs, thermal performance data, SOT-223 package layout, real-world load/line regulation behavior, and validated drop-in alternatives for industrial and automotive power design.

Technical Context

The LD1117S50TR uses an NPN pass transistor architecture, enabling high efficiency by routing quiescent current primarily into the load rather than ground - unlike PNP-based regulators. Its internal bandgap reference and trimming circuitry achieve tight output accuracy without external components.

It integrates thermal shutdown and current limiting, operates across -40 °C to +125 °C junction temperature, and requires only a single 10 µF ceramic output capacitor for stability - eliminating need for ESR-sensitive tantalum or electrolytic types.

Key Specifications

Pinout & Package

SOT-223 package with exposed thermal pad connected internally to V_OUT; compact 3-pin surface-mount footprint optimized for thermal performance and PCB space savings in dense layouts.

Key Features

Applications

Equivalent & Alternatives

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

Compared with TLV1117-50CDR and MCP1703T-5002E/MB, the LD1117S50TR uniquely balances 800 mA capability, 1.0 V dropout, SOT-223 thermal robustness, and ±1 % accuracy - making it optimal for cost-sensitive, thermally constrained 5 V system rails requiring reliability across extended temperature ranges.

Availability

LD1117S50TR is available at Aetrix Electronics and suitable for industrial PLCs, automotive body control units, medical sensor modules, and smart energy metering hardware requiring stable component supply and long-lifecycle support.

Supply support for LD1117S50TR 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, power, microcontroller, and sensor solutions for industrial, automotive, and consumer markets.

The LD1117 series belongs to ST's general-purpose linear regulator product line, engineered for high-reliability, low-cost power management in space-constrained and thermally demanding applications across industrial automation and automotive electronics.

FAQ

What is the minimum input voltage required for stable 5 V output at 800 mA?

The LD1117S50TR requires a minimum input-to-output differential of 1.10 V at 800 mA (per datasheet Table 7). Therefore, stable 5.0 V output demands VIN ≥ 6.10 V under full load. At lighter loads (e.g., 100 mA), 6.0 V suffices due to 1.0 V typical dropout. Input below 6.1 V risks dropout and unregulated output.

Can the LD1117S50TR replace the older LD1117AS50TR in existing designs?

Yes - LD1117S50TR is a direct replacement for LD1117AS50TR, sharing identical pinout, electrical specs, and SOT-223 package. The "S" suffix denotes the standard version (vs. "AS" for automotive-grade), but both meet the same ±1 % tolerance at 25 °C and 800 mA output capability. No layout or firmware changes are needed.

Is an input capacitor required, and what value is recommended?

An input capacitor is strongly recommended to suppress high-frequency noise and transient spikes from upstream sources. ST specifies a minimum 10 µF ceramic capacitor (X5R/X7R, 10 V rating) placed within 5 mm of the V_IN pin. Larger values (22–47 µF) improve transient response but are not mandatory for basic stability.

Does the SOT-223 thermal pad require solder paste stencil optimization?

Yes - the exposed thermal pad (Pin 1/Tab) must be fully soldered to a dedicated copper pour for thermal conduction. ST recommends a 0.3–0.4 mm stencil aperture with 70–80 % paste coverage and at least 4 thermal vias (0.3 mm diameter, filled or capped) connecting to inner/ground planes. Inadequate pad soldering raises R_thJA beyond 110 °C/W, risking thermal shutdown above 400 mA.