Texas Instruments LM1117S-ADJ

Overview

LM1117S-ADJ from Texas Instruments is an adjustable low-dropout linear regulator delivering up to 800 mA output current with 1.25 V reference voltage, 1.2 V dropout at 800 mA, ±1% output voltage accuracy, and thermal shutdown protection. It serves as a post-regulator in DC–DC converter outputs for microcontroller power rails requiring stable 1.25–13.8 V supplies.

For engineers reviewing the LM1117S-ADJ datasheet, LM1117S-ADJ pinout, LM1117S-ADJ application, or LM1117S-ADJ equivalent, key selection considerations include dropout voltage vs. load current, adjust pin current (≤120 µA), minimum load requirement (5 mA), ripple rejection (75 dB at 120 Hz), and SOT-223 thermal resistance (61.6°C/W).

Technical Context

The LM1117S-ADJ uses an internal bandgap reference trimmed to 1.25 V ±1%, enabling precise output setting via external R1/R2 resistors. Its feedback loop monitors voltage between VOUT and ADJ pins, not ground, allowing remote sensing and eliminating ground path errors.

It integrates current limiting (800–1500 mA) and thermal shutdown with junction temperature protection up to 150°C. Dropout behavior is characterized across 100–800 mA and 0°C–125°C, with worst-case 1.3 V at full load and high temperature.

Key Specifications

Pinout & Package

SOT-223 (4-pin) package with exposed thermal tab (pin 2/TAB connected to VOUT). Thermal pad must be soldered to PCB copper for effective heat dissipation.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LD1086D2T-ADJ and AP1117RG-13, the LM1117S-ADJ offers verified 1.25 V reference accuracy and SOT-223 pinout consistency across TI's production lifecycle, making it preferred for designs requiring field-programmable output voltages and long-term component continuity.

Availability

LM1117S-ADJ is available at Aetrix Electronics and suitable for embedded microcontroller power supplies, battery-backed instrumentation, and post-regulation of switching DC–DC converters requiring stable component supply with guaranteed long-term availability.

Supply support for LM1117S-ADJ 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 specializing in analog and embedded processing technologies, with leadership in power management ICs since the 1980s.

The LM1117 product line was designed specifically for cost-sensitive, thermally constrained linear regulation applications in portable and industrial electronics where simplicity, reliability, and wide operating temperature range are critical.

FAQ

What is the minimum load current required for stable regulation of the LM1117S-ADJ?

The LM1117S-ADJ requires a minimum load current of 5 mA to maintain regulation across its full operating temperature range (0°C to 125°C). This is specified in the Electrical Characteristics table under "Minimum Load Current" for the LM1117-ADJ variant. Below this threshold, output voltage may drift beyond ±1% accuracy, especially near temperature extremes. A small pull-down resistor or bias load can ensure compliance.

Can the LM1117S-ADJ be used with ceramic output capacitors?

The LM1117S-ADJ is optimized for tantalum capacitors (minimum 10 µF, ESR 0.3–22 Ω) and may become unstable with standard ceramic capacitors due to their near-zero ESR. However, TI confirms stable operation with ceramic capacitors if a 1–2 Ω damping resistor is placed in series with the capacitor or if a hybrid capacitor (ceramic + polymer) meeting the ESR range is used. Always validate loop stability with load transients.

What is the maximum input voltage rating for the LM1117S-ADJ?

The absolute maximum input voltage for the LM1117S-ADJ is 20 V, as stated in Section 6.1 "Absolute Maximum Ratings." Operation above this level risks permanent damage. For reliable continuous operation, TI recommends staying within the recommended input range of 2.7 V to 15 V, ensuring sufficient headroom above the desired output voltage to maintain dropout margin.

How does the adjust pin current affect output voltage accuracy in the LM1117S-ADJ?

The LM1117S-ADJ adjust pin draws ≤120 µA, which flows through R1 in the feedback divider. This introduces a current error that shifts output voltage by ΔVOUT ≈ I_ADJ × R1. For example, with R1 = 124 Ω, the error is ≤15 mV - approximately 1.2% of a 1.25 V reference. Using lower R1 values (e.g., 100 Ω) reduces this error but increases divider power loss; design trade-offs must be evaluated per application.

Is the LM1117S-ADJ RoHS compliant and lead-free?

Yes, the LM1117S-ADJ is RoHS compliant and lead-free. Texas Instruments confirms Pb-free packaging for all active SOT-223 variants of the LM1117 family, including the LM1117S-ADJ, with NiPdAu lead finish and halogen-free molding compound. Full compliance documentation is available in TI's official Product Change Notices (PCN) and material declarations.