STMicroelectronics LD1117S28TR

Overview

LD1117S28TR from STMicroelectronics is a fixed-output 2.85 V low-dropout linear voltage regulator in SOT-223 package, delivering up to 800 mA output current with 1.0 V typical dropout at 100 mA, ±1 % output voltage tolerance at 25 °C, and 75 dB supply voltage rejection at 120 Hz. It serves as a primary post-regulator in industrial power rails, USB-powered peripherals, and embedded microcontroller supply domains.

For engineers reviewing the LD1117S28TR datasheet, LD1117S28TR pinout, LD1117S28TR application, or LD1117S28TR equivalent, this page delivers verified electrical specs, thermal performance data, real-world load/line regulation behavior, and validated alternative options for 2.8–3.0 V LDO replacement scenarios.

Technical Context

The LD1117S28TR uses an NPN pass transistor architecture to minimize quiescent current consumption-most of the bias current flows into the load rather than being wasted as ground current. Its internal bandgap reference (1.25 V) and trimming circuitry enable tight ±1 % output accuracy over temperature and line/load variations.

Stability requires only a 10 µF ceramic or tantalum output capacitor; no ESR constraints apply. Thermal shutdown and current limiting are integrated, with junction-to-case thermal resistance of 15 °C/W in SOT-223 enabling 800 mA operation under moderate ambient conditions without heatsinking.

Key Specifications

Pinout & Package

SOT-223 package with exposed thermal pad connected internally to VOUT; 3-pin configuration optimized for surface-mount thermal management and PCB space efficiency.

Key Features

Applications

Equivalent & Alternatives

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

Compared with AMS1117-2.85, LD1117S28TR provides superior accuracy and ripple rejection for noise-sensitive applications; versus TLV70228, it trades off quiescent current for 4× higher output capability and robust thermal performance in SOT-223.

Availability

LD1117S28TR is available at Aetrix Electronics and suitable for industrial sensor nodes, USB-powered peripherals, embedded controller core rails, and FPGA I/O bank regulation requiring stable component supply across long-lifecycle production programs.

Supply support for LD1117S28TR 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 consumer markets.

The LD1117 series was engineered as a cost-optimized, thermally robust LDO family targeting high-volume embedded power applications where reliability, simplicity, and wide input range outweigh ultra-low IQ requirements.

FAQ

What is the minimum output capacitor required for stability?

The LD1117S28TR is stable with a minimum 10 µF ceramic or tantalum capacitor on the output. No ESR specification is required-unlike many older LDOs, it does not depend on capacitor ESR for phase margin. X5R/X7R dielectrics are recommended for temperature stability.

Can LD1117S28TR replace a 3.3 V regulator in the same footprint?

No-LD1117S28TR is a 2.85 V fixed-output device and is not pin-compatible with 3.3 V variants like LD1117S33TR. While both use SOT-223, output voltage is laser-trimmed during manufacturing and cannot be altered. Substitution requires board-level redesign and validation of downstream voltage tolerances.

Does it require an input capacitor?

An input capacitor is not strictly required for stability but is strongly recommended: a 1 µF ceramic capacitor placed within 5 mm of the VIN pin suppresses high-frequency noise and improves transient response. Without it, line transients may cause output overshoot or instability under fast load steps.

What is the maximum allowable power dissipation in SOT-223 without a heatsink?

With R_thJA = 110 °C/W (typical on 1-layer FR4), maximum safe dissipation at T_A = 25 °C is ~1.1 W (P_D = (125 − 25)/110). At 800 mA and 1.1 V dropout, power dissipation is 0.88 W-within safe limits. For continuous 800 mA operation above 50 °C ambient, a thermal pad or small copper area is advised.