Texas Instruments LM1117IMPX-3.3

Overview

LM1117IMPX-3.3 from Texas Instruments is a fixed-output, 3.3 V, 800 mA low-dropout linear regulator in SOT-223 package, featuring ±1% output voltage accuracy over 0°C to +125°C, 1.2 V dropout at 800 mA, and integrated thermal shutdown and current limiting. It delivers stable power for microprocessor core supplies and post-regulation in DC/DC converter outputs.

For engineers reviewing the LM1117IMPX-3.3 datasheet, LM1117IMPX-3.3 pinout, LM1117IMPX-3.3 application, or LM1117IMPX-3.3 equivalent, key selection factors include guaranteed 3.3 V output tolerance (±1%), minimum 4.75 V input requirement, 10 µF tantalum output capacitor stability requirement, and SOT-223 thermal resistance (61.6°C/W).

Technical Context

The LM1117IMPX-3.3 uses a Zener-trimmed band-gap reference for precise 3.3 V regulation and incorporates internal current limiting and thermal protection circuitry. Its architecture supports stable operation with only a 10 µF tantalum output capacitor and requires no external components for basic functionality.

It operates across an input voltage range of 4.75 V to 15 V and maintains load regulation within 0.4% maximum over 0–800 mA output current and temperature range 0°C to +125°C. Dropout voltage is specified at 1.2 V (max) at full 800 mA load and 125°C junction temperature.

Key Specifications

Pinout & Package

SOT-223 (DCY) package: 4-pin thermally enhanced surface-mount outline with exposed thermal pad (pin 4 = tab/VOUT). Body size 6.50 mm × 3.50 mm. Pin 1 = ADJ/GND (ground for fixed-output variants), Pin 2 = VOUT, Pin 3 = VIN, Pin 4 = VOUT (tab connection).

Key Features

Applications

Equivalent & Alternatives

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

Compared with LM1117IMPX-3.3, TLV76133 enables longer battery life and lower dropout but sacrifices industrial temperature support, while TLV1117-33 provides broader environmental qualification and better high-frequency PSRR-both require validation of thermal performance under identical layout and load conditions.

Availability

LM1117IMPX-3.3 is available at Aetrix Electronics and suitable for industrial AC/DC power supplies, ultrasound scanners, servo drive control modules, and merchant network/server PSU requiring stable component supply and long-term manufacturability.

Supply support for LM1117IMPX-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 and embedded processing chips for industrial, automotive, and communications markets.

The LM1117 product line delivers cost-effective, thermally robust linear regulators for post-regulation and low-noise biasing in space-constrained applications where simplicity and reliability are prioritized over ultra-low IQ or ultra-low dropout.

FAQ

What is the minimum input voltage required for stable operation of the LM1117IMPX-3.3?

The LM1117IMPX-3.3 requires a minimum input voltage of 4.75 V to maintain regulation at full 800 mA load and 125°C junction temperature, based on its 1.2 V maximum dropout specification. At room temperature and light loads, operation may be possible down to ~4.55 V, but design margin must account for worst-case dropout and input ripple. The LM1117IMPX-3.3 datasheet specifies 4.75 V as the absolute minimum recommended input under full-load, high-temperature conditions.

Does the LM1117IMPX-3.3 require an external capacitor on the adjust pin?

No-the LM1117IMPX-3.3 is a fixed-output variant, so the ADJ pin is internally connected to ground and does not require external components. Unlike the adjustable LM1117-ADJ version, the LM1117IMPX-3.3 has R1 and R2 integrated internally. The device only requires a minimum 10 µF tantalum capacitor on the output and a recommended 10 µF input capacitor for stable operation. Adding capacitance to the ADJ pin on the LM1117IMPX-3.3 is unnecessary and unsupported.

Can the LM1117IMPX-3.3 be used in automotive applications?

The standard LM1117IMPX-3.3 is rated for 0°C to +125°C junction temperature and is not AEC-Q100 qualified. It lacks automotive-specific stress testing, failure-in-time (FIT) data, and extended temperature validation. While it may function in under-hood environments with sufficient derating and heatsinking, TI does not recommend or guarantee the LM1117IMPX-3.3 for automotive applications. For such use cases, consider the automotive-grade TLV1117-33Q or TPS7A83A-Q1 instead.

What thermal considerations apply to the LM1117IMPX-3.3 in SOT-223 package?

The LM1117IMPX-3.3 in SOT-223 has a junction-to-ambient thermal resistance (RθJA) of 61.6°C/W with standard JEDEC 2-layer board layout. At 800 mA output and 5 V input (2.4 W dissipation), junction temperature rise exceeds 148°C-exceeding the 125°C limit. Successful thermal design requires a large copper pour connected to the tab (Pin 4), multiple thermal vias to inner layers, and ambient temperature control. Derating to ≤500 mA or using forced air is recommended for continuous full-load operation without heatsink.

Is the LM1117IMPX-3.3 pin-compatible with other SOT-223 LDOs like the MIC29302?

No-the LM1117IMPX-3.3 is not pin-compatible with MIC29302 or most other SOT-223 LDOs. While all share the same physical outline, pin assignments differ: LM1117IMPX-3.3 uses Pin 1 = GND, Pin 2 = VOUT, Pin 3 = VIN, Pin 4 = VOUT (tab); MIC29302 uses Pin 1 = VIN, Pin 2 = GND, Pin 3 = VOUT, Pin 4 = tab/GND. Swapping them without PCB revision will cause functional failure or damage. Always verify pinout diagrams before substitution-even within the same package type.