STMicroelectronics LD1117S18CTR

Overview

LD1117S18CTR from STMicroelectronics is a fixed-output 1.8 V low-dropout linear voltage regulator delivering up to 800 mA, featuring 1 V typical dropout at 100 mA, ±1 % output voltage tolerance at 25 °C, and 75 dB supply voltage rejection at 120 Hz - deployed in power rails for microcontrollers, sensors, and USB peripherals requiring stable low-voltage bias.

For engineers reviewing the LD1117S18CTR datasheet, LD1117S18CTR pinout, LD1117S18CTR application, or LD1117S18CTR equivalent, this page delivers verified package mapping (SOT-223), thermal resistance (R_thJC = 15 °C/W), minimum load current (2–5 mA), quiescent current (5–10 mA), and stability condition (10 µF output capacitor).

Technical Context

The LD1117S18CTR uses an NPN pass transistor architecture to minimize quiescent current consumption in the load path, enabling high efficiency under light-load conditions. Its internal bandgap reference and trimming circuitry achieve tight output regulation across temperature and line/load variations.

It integrates thermal shutdown and current limiting for fault protection, operates with only a 10 µF ceramic or tantalum output capacitor for stability, and maintains specified performance over –40 °C to +125 °C junction temperature range in the C-grade version.

Key Specifications

Pinout & Package

SOT-223 package with exposed thermal tab electrically connected to V_OUT; compact surface-mount footprint optimized for thermal performance 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 MIC29302WU-1.8 and TLV70118DBVR, the LD1117S18CTR balances 800 mA capability, 1 V dropout, integrated protection, and SOT-223 thermal performance - making it optimal for cost-sensitive industrial and embedded designs requiring reliability at moderate load currents.

Availability

LD1117S18CTR is available at Aetrix Electronics and suitable for industrial sensor nodes, USB peripheral power supplies, embedded microcontroller cores, and FPGA I/O banks requiring stable component supply with long-term manufacturability.

Supply support for LD1117S18CTR 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 specializing in power management, microcontrollers, and analog ICs, with manufacturing facilities across Europe and Asia.

The LD1117 series belongs to ST's general-purpose linear regulator product line, designed for cost-effective, thermally robust voltage regulation in industrial, consumer, and computing applications.

FAQ

What is the minimum input voltage required for stable 1.8 V output at 800 mA?

The LD1117S18CTR requires at least 2.9 V input (1.8 V + 1.1 V max dropout at 800 mA) for full-load regulation. At 100 mA, 2.8 V suffices due to 1.0 V typical dropout. Input below 2.8 V causes output collapse or unregulated behavior.

Can the LD1117S18CTR be used without an output capacitor?

No. A minimum 10 µF output capacitor is mandatory for stability per the datasheet. Omitting it causes oscillation or thermal runaway. Ceramic, tantalum, or aluminum electrolytic types are acceptable if ESR falls within 0.1–10 Ω range.

Does the SOT-223 thermal tab require a solder connection to PCB ground?

The tab is internally connected to V_OUT, not GND. It must be soldered to a dedicated copper pour tied to the 1.8 V output net - not system ground - to ensure thermal conduction and avoid shorting V_OUT to GND.

How does the LD1117S18CTR handle reverse polarity on the input pin?

It has no reverse-polarity protection. Applying negative voltage to V_IN forward-biases the substrate diode between V_IN and GND, causing high current flow and potential destruction. External series diode or MOSFET protection is required in reverse-voltage-prone systems.