STMicroelectronics LD1117F33C

Overview

LD1117F33C 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 post-regulation in microcontroller power supplies, industrial sensors, and embedded USB peripherals.

For engineers reviewing the LD1117F33C datasheet, LD1117F33C pinout, LD1117F33C application, or LD1117F33C equivalent, this page provides verified package mapping (SOT-223), thermal resistance data (R_thJA = 110 °C/W), minimum 10 µF output capacitor requirement, and confirmed drop-in compatibility with other LD1117 fixed-voltage variants in same package.

Technical Context

The LD1117F33C employs an NPN pass transistor architecture, enabling high efficiency by routing quiescent current primarily into the load rather than ground. Its internal bandgap reference and error amplifier maintain regulation across input voltages from 4.75 V to 15 V and junction temperatures from –40 °C to +125 °C.

Thermal protection and current limiting are implemented on-die, with thermal regulation of 0.01–0.1 %/W and guaranteed safe operation up to 12 W power dissipation. The device requires only a single 10 µF ceramic or tantalum output capacitor for stability - no bypass or feedforward capacitors needed.

Key Specifications

Pinout & Package

LD1117F33C is supplied in SOT-223 package (TO-261AA), with exposed thermal pad electrically connected to V_OUT. Pin 1 = Input, Pin 2 = Ground, Pin 3 = Output, Pin 4 = Tab (V_OUT).

Key Features

Applications

Equivalent & Alternatives

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

Compared with AMS1117-3.3 and TLV1117-33, LD1117F33C delivers superior output accuracy (±1 %), higher guaranteed current (800 mA), and full industrial temperature support (–40 to +125 °C), making it optimal for mission-critical embedded power rails where regulation stability and thermal resilience are non-negotiable.

Availability

LD1117F33C is available at Aetrix Electronics and suitable for industrial automation controllers, automotive body electronics, and medical diagnostic equipment requiring stable component supply and long-term manufacturing continuity.

Supply support for LD1117F33C 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.

LD1117 belongs to ST's standard linear regulator product line, engineered for cost-sensitive, high-reliability applications demanding tight tolerance, robust thermal behavior, and minimal external components in space-constrained designs.

FAQ

Can LD1117F33C be used with input voltage below 4.75 V?

No. The absolute minimum input voltage is defined by dropout: for 3.3 V output, VIN must exceed 4.4 V (3.3 V + 1.1 V) to sustain 800 mA. Below 4.75 V, output current capability degrades rapidly; operation below 4.4 V results in unregulated output. Datasheet specifies 4.75 V as minimum recommended input for full-spec performance.

Is a heatsink required for continuous 800 mA operation in SOT-223?

Yes - with R_thJA = 110 °C/W, 800 mA at 1.1 V dropout dissipates 0.88 W, causing ~97 °C rise above ambient. At 25 °C ambient, junction temperature reaches ~122 °C - near the 125 °C limit. A minimum 1 cm² copper pour on top layer is mandatory; larger thermal pads or internal planes are strongly advised for reliability.

Does LD1117F33C require an input capacitor?

While not strictly mandatory for stability, ST recommends ≥1 µF ceramic capacitor at the IN pin to suppress high-frequency noise and prevent oscillation under dynamic load changes. Without it, PSRR degrades above 10 kHz and startup overshoot may exceed 5 %, risking downstream logic damage in sensitive applications.

How does LD1117F33C behave during short-circuit events?

The device features foldback current limiting and thermal shutdown. Under sustained short, output current drops to ~200 mA while junction temperature rises; at ~165 °C, thermal shutdown activates, cutting output. Recovery occurs automatically after cooldown (~10–30 s). No latch-up or damage occurs within absolute maximum ratings.