Texas Instruments LMS8117ADT-3.3

Overview

LMS8117ADT-3.3 from Texas Instruments is a fixed-output, 3.3-V, 1-A low-dropout linear regulator in SOT-223 package, featuring ±1% output voltage accuracy, 1.25-V dropout at 1 A, and integrated thermal shutdown and current limiting. It serves as a post-regulator for DC-DC converters and local power supply for microcontrollers and analog circuitry.

For engineers reviewing the LMS8117ADT-3.3 datasheet, LMS8117ADT-3.3 pinout, LMS8117ADT-3.3 application, or LMS8117ADT-3.3 equivalent, key selection criteria include guaranteed 3.3-V output tolerance (±1%), minimum 10-µF tantalum output capacitance requirement, dropout performance across 0°C to 125°C, and compatibility with standard LM317 PCB footprints.

Technical Context

The LMS8117ADT-3.3 implements a Zener-trimmed band-gap reference for precise 3.3-V regulation and uses internal PNP pass transistor architecture enabling low dropout. Its protection circuitry includes foldback current limiting and thermal shutdown triggered at ~150°C junction temperature.

It operates with input voltages from 4.75 V to 15 V, maintains load regulation within ±0.4% over 0–1 A, and achieves line regulation ≤6 mV across its operating input range. The device requires no external feedback resistors and is pin-compatible with the LM317 in fixed-voltage configuration.

Key Specifications

Pinout & Package

SOT-223 (DCY) 4-pin package with exposed thermal pad (Pin 4 = OUTPUT); body size 3.50 mm × 6.50 mm; lead-free and RoHS compliant.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LM1117MPX-3.3/NOPB and TLV1117-33CDCYR, the LMS8117ADT-3.3 delivers tighter output accuracy (±1% vs ±2%), higher output current (1 A vs 800 mA), and proven stability with low-ESR tantalum output caps - making it optimal for noise-sensitive industrial and instrumentation applications where regulation precision and transient immunity are critical.

Availability

LMS8117ADT-3.3 is available at Aetrix Electronics and suitable for industrial control systems, battery-powered instrumentation, and embedded microcontroller power supplies requiring stable component supply and long-term lifecycle support.

Supply support for LMS8117ADT-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 leader specializing in analog, embedded processing, and power management technologies, with decades of expertise in high-reliability linear regulators.

The LMS8117A product line was designed specifically for industrial and embedded applications demanding robust thermal performance, tight DC accuracy, and drop-in compatibility with legacy LM317 layouts - targeting post-regulation, battery charging, and local point-of-load use cases.

FAQ

What is the minimum input voltage required for LMS8117ADT-3.3 to maintain regulation?

The LMS8117ADT-3.3 requires a minimum input-to-output differential of 1.25 V at 1 A load to remain in regulation. Therefore, with a nominal 3.3-V output, the absolute minimum input voltage is 4.55 V. At lighter loads, dropout decreases - e.g., 1.1 V at 100 mA - allowing operation down to ~4.4 V under typical conditions. This value is validated across 0°C to 125°C junction temperature.

Can LMS8117ADT-3.3 be used with ceramic output capacitors instead of tantalum?

The LMS8117ADT-3.3 is characterized and guaranteed stable with ≥10-µF tantalum capacitors having 0.5–5 Ω ESR. While some ceramic capacitors may work in specific layouts, TI does not guarantee stability with ceramics due to their near-zero ESR, which can induce oscillation. For ceramic-compatible alternatives, consider the TLV1117-33CDCYR, which is explicitly qualified for 10-µF ceramic output caps.

Is LMS8117ADT-3.3 pin-compatible with the LM317 in fixed-voltage applications?

Yes - the LMS8117ADT-3.3 uses the same 3-pin SOT-223 footprint and pinout (Input, Output, GND) as the LM317 configured for fixed output, enabling direct PCB replacement without layout changes. However, unlike the LM317, the LMS8117ADT-3.3 integrates the feedback network internally and does not require external resistors, simplifying bill-of-materials and reducing component count.

Does LMS8117ADT-3.3 require an input bypass capacitor?

TI recommends a 10-µF tantalum input capacitor for the LMS8117ADT-3.3, especially when the regulator is located more than 2 cm from the main power supply filter. This capacitor mitigates input impedance effects and improves transient response to upstream supply disturbances. The requirement is documented in Section 8.2.1.2.1.1 of the official SNOS487F datasheet.

What thermal considerations apply when using LMS8117ADT-3.3 at full 1-A load?

At 1 A and 4.75-V input (1.45-W dissipation), the LMS8117ADT-3.3 in SOT-223 (RθJA = 61.4°C/W) will rise ~89°C above ambient. With 25°C ambient, junction temperature reaches ~114°C - within the 125°C limit but leaving <11°C margin. Adequate copper pour under the thermal pad and airflow are essential; for continuous 1-A operation above 40°C ambient, thermal simulation or derating is advised.