Texas Instruments LM1117T-3.3

Overview

LM1117T-3.3 from Texas Instruments is a fixed-output 3.3 V, 800 mA low-dropout linear regulator in TO-220 package, featuring 1.2 V dropout at 800 mA load, ±1% output voltage accuracy over 0°C to 125°C, and integrated thermal shutdown and current limiting. It serves as a post-regulator for DC–DC converters and powers microprocessor core logic in embedded systems.

For engineers reviewing the LM1117T-3.3 datasheet, LM1117T-3.3 pinout, LM1117T-3.3 application, or LM1117T-3.3 equivalent, key selection considerations include dropout voltage at full load, thermal resistance (R_θJA = 23.8°C/W), minimum output capacitance (10 µF tantalum), line regulation (≤6 mV), and compatibility with standard TO-220 heatsinking solutions.

Technical Context

The LM1117T-3.3 uses a bandgap reference trimmed with Zener diodes to maintain ±1% output accuracy across temperature and load. Its internal PNP pass transistor enables low dropout operation while supporting stable regulation with only 10 µF output capacitance.

Thermal protection activates when junction temperature exceeds 150°C, and current limiting holds output current at 800–1500 mA depending on input-output differential. The device operates without external protection diodes under normal conditions but requires an external VIN-to-VOUT diode if the input is shorted while a large output capacitor discharges.

Key Specifications

Pinout & Package

LM1117T-3.3 is housed in a 3-pin TO-220 package (14.986 mm × 10.16 mm body) with tab-connected VOUT for enhanced thermal conduction. The tab is electrically connected to the output pin and must be isolated from chassis ground unless output ground is chassis-referenced.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar linear regulator applications.

Compared with LM1117T-3.3, the SOT-223 variant trades thermal performance for size, while the TLV1117 offers lower dropout and quiescent current in a smaller package - both require layout and thermal reassessment but deliver identical 3.3 V regulation functionality.

Availability

LM1117T-3.3 is available at Aetrix Electronics and suitable for industrial control systems, embedded instrumentation, and power management subsystems requiring stable component supply, long-term lifecycle support, and traceable sourcing.

Supply support for LM1117T-3.3 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

Texas Instruments is a global semiconductor company headquartered in Dallas, Texas, designing and manufacturing analog ICs, embedded processors, and high-performance power management solutions.

The LM1117 product line delivers cost-effective, thermally robust linear regulators for post-regulation, battery charging, and low-noise system rails - engineered for reliability in industrial, computing, and portable applications.

FAQ

What is the maximum input voltage rating for LM1117T-3.3?

The absolute maximum input voltage for LM1117T-3.3 is 20 V, but the recommended operating range is 4.75 V to 15 V. Exceeding 15 V increases power dissipation and thermal stress without functional benefit. The device's 1.2 V dropout means VIN must remain ≥4.5 V to sustain 3.3 V output at full 800 mA load. Operation above 15 V should be avoided unless transient surge protection is implemented.

Does LM1117T-3.3 require an input capacitor?

Yes, LM1117T-3.3 requires an input bypass capacitor - a 10 µF tantalum capacitor is recommended for most applications. This capacitor stabilizes the input rail during transient load changes and prevents oscillation caused by source impedance. While not strictly mandatory for basic regulation, omitting it risks instability, especially when powered from long traces or high-impedance sources like battery packs or unregulated wall adapters.

Can LM1117T-3.3 be used without a heatsink?

LM1117T-3.3 can operate without an external heatsink at ≤300 mA load and ≤+50°C ambient temperature, based on its R_θJA of 23.8°C/W. At full 800 mA with 5 V input (1.7 W dissipation), junction temperature rises ~40°C above ambient - exceeding safe limits without heatsinking. For continuous 800 mA operation, a minimum 10 cm² aluminum heatsink or PCB copper pour is required to maintain TJ ≤125°C.

What output capacitor is required for stable operation of LM1117T-3.3?

A minimum 10 µF tantalum capacitor is required at the output of LM1117T-3.3 to ensure stability and transient response. The capacitor must have ESR between 0.3 Ω and 22 Ω. Ceramic capacitors may be used only if their effective ESR is within this range - often requiring intentional series resistance. Larger capacitance (e.g., 22 µF) improves load step response but does not reduce minimum ESR requirements.

Is LM1117T-3.3 compatible with lead-free reflow soldering processes?

Yes, LM1117T-3.3 in TO-220 package is rated for lead-free reflow per JEDEC J-STD-020. Its peak reflow temperature tolerance is 260°C for 10 seconds. The device meets RoHS and REACH compliance requirements. Proper thermal profiling is essential to avoid thermal shock - ramp rates should not exceed 3°C/s, and time above 217°C must be limited to 60–150 seconds to prevent die attach degradation or bond wire fatigue.