STMicroelectronics LD1117AS33TR

LD1117AS33TR by STMicroelectronics Summary and Description

In modern electronics design, the simplicity and reliability of power management components are vital for both prototyping and large-scale manufacturing. The LD1117AS33TR from STMicroelectronics stands out as a fixed, positive 3.3V, 1A low dropout linear voltage regulator, designed to deliver robust performance with minimal external components. Housed in the compact SOT-223 surface-mount package, the device combines high efficiency, tight voltage regulation, and on-chip protection features, making it a staple in microcontroller, logic, and digital system supplies.

Main Attributes of LD1117AS33TR

The LD1117AS33TR distinguishes itself with several core features tailored for efficient and dependable operation:

Low Dropout Voltage: With a typical dropout of 1.15V at a full 1A load (at 25°C), the LD1117AS33TR supports applications where input-to-output voltage difference is limited, maximizing usable power from tight supply rails.

Low Quiescent Current: Consuming only 5mA typical at room temperature, the device minimizes self-heating and power loss in batteryor energy-sensitive systems.

Output Current Capability: The regulator supports up to 1A output, suitable for moderate power requirements such as sensors, communication modules, or interface logic.

Fixed 3.3V Output: This variant provides a well-regulated fixed output ideal for processors and digital logic that require 3.3V rails.

Tight Output Tolerance: Thanks to chip-level trimming, the LD1117AS33TR achieves ±2% voltage accuracy at 25°C, ensuring downstream circuit performance consistency.

Internal Protections: Integrated current and thermal limit mechanisms safeguard not only the device but also the system against overloads and overheating.

High Supply Voltage Rejection: Typical 80dB rejection at 25°C ensures supplies remain clean, preserving downstream signal integrity.

Temperature Range: Qualified for operation from 0°C to 125°C, the device performs reliably across a broad range of environmental conditions.

Electrical Specifications and Performance Overview

At the heart of the LD1117AS33TR's robust regulation lies its precise reference sources and NPN pass transistor design. The regulator delivers a stable 3.3V at loads up to 1A when both input and output capacitors (10μF typical) are used to ensure stability. Voltage accuracy remains within ±2% at 25°C, and tolerance extends to ±4% across the full specified temperature range. High supply voltage rejection, up to 80dB, enables it to effectively filter noisy inputs—a frequent requirement in embedded systems. The combination of low dropout and minimal quiescent current delivers efficient power conversion for applications powered via multi-stage or battery-drops.

For engineers anticipating worst-case scenarios, it is crucial to note the device’s absolute maximum ratings must not be exceeded, as permanent damage may result. In thermal and short-circuit events, the LD1117AS33TR’s protection circuits actively safeguard against failure, bolstering design robustness.

Common Uses of LD1117AS33TR

The LD1117AS33TR linear regulator excels in designs where stable 3.3V power is imperative and board space is at a premium. Typical applications include:

Powering microcontrollers, FPGAs, and logic devices with 3.3V requirements.

Post-regulation of DC-DC converters to reduce ripple or improve accuracy.

Local point-of-load regulation for high-noise environments in digital systems.

Consumer electronics, industrial measurement, and sensor subsystems.

Wireless modules, networking equipment, and interface bridges.

Designers commonly use the LD1117AS33TR for cost-effective voltage regulation in mixed-signal and digital boards, where regulated 3.3V rails must be derived from higher supply voltages (such as 5V or the unregulated output of a wall adapter).

Design Guidelines for Working with LD1117AS33TR

Optimizing the performance of the LD1117AS33TR requires careful attention to board layout, component selection, and application-specific constraints:

Input and Output Capacitors: The device requires only a standard 10μF capacitor on both input and output for stability, simplifying component sourcing and BOM complexity.

Board Layout: For minimized output noise and optimal regulation, place the output capacitor close to the regulator’s VOUT pin and connect grounds with low impedance traces.

Thermal Management: Despite the SOT-223 package’s relatively good thermal performance, ensure adequate copper area or heatsinking for applications approaching the 1A current rating, particularly in warm environments.

Protection/Circuit Safety: The internal current and thermal limiting functions help prevent damage in the event of overloads, but board-level fusing or further protection may be necessary for mission-critical applications.

LD1117AS33TR Packaging Options and Physical Specifications

Engineers seeking high-density board layouts benefit from the LD1117AS33TR’s SOT-223 package, offering:

Compact, low-profile footprints for surface-mount assembly.

Optimized thermal path via the large tab (connected to VOUT) that facilitates heat dissipation into the PCB.

Fully documented tape-and-reel data for automated assembly.

Exact dimensions and land pattern recommendations specified for reliable soldering and mechanical integration.

Device variants are also available in DPAK and TO-220 packages, offering flexibility for differing assembly and power dissipation requirements.

Regulatory and Environmental Information for LD1117AS33TR

The LD1117AS33TR demonstrates strong environmental compliance:

RoHS3 Compliant: Ensures no restricted substances, compatible with global green manufacturing initiatives.

REACH Unaffected: Meets European chemicals regulation standards.

Moisture Sensitivity Level 1: Supports unlimited floor life at ≤30°C/85% RH, easing storage and assembly logistics.

The device also conforms to standard export control classifications (ECCN: EAR99) and harmonized tariff codes for international shipment.

Alternative or Substitute Products for LD1117AS33TR

When evaluating the LD1117AS33TR for new designs or legacy replacements, engineers may consider similar devices within STMicroelectronics’ LD1117A series, which offer fixed output voltages of 1.2V, 1.8V, or adjustable versions (with 1.25V reference). Additionally, equivalents in SOT-223 or other power packages, with comparable pinouts, voltage tolerances, and protection features, should be considered based on system requirements. Always verify electrical and thermal characteristics to ensure compatibility.

Conclusion

The LD1117AS33TR from STMicroelectronics remains a highly practical solution for stable, efficient 3.3V power regulation in a broad spectrum of electronic applications. Its balance of low dropout voltage, robust current handling, integrated protections, and space-saving package targets the needs of modern embedded design, while alignment with environmental and industry standards ensures sustained relevance in procurement selections. For engineers and buyers alike, the LD1117AS33TR offers a well-vetted, reliable building block for contemporary power architectures.