Texas Instruments LM1117T-ADJ

Overview

LM1117T-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 for DC–DC converters in embedded power rails requiring stable 1.25–13.8 V outputs.

For engineers reviewing the LM1117T-ADJ datasheet, LM1117T-ADJ pinout, LM1117T-ADJ application, or LM1117T-ADJ equivalent, key selection criteria include dropout voltage vs. load, ADJ-pin current tolerance (≤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 LM1117T-ADJ uses an internal bandgap reference trimmed to 1.25 V with ±1% initial accuracy and 0.5% temperature stability over 0°C to 125°C. Its error amplifier compares the ADJ-to-VOUT voltage against this reference to control the pass transistor.

It integrates current limiting (800–1500 mA) and thermal shutdown with automatic recovery. The ADJ pin draws only 60 µA typical, enabling precise resistor-divider-based output programming while minimizing regulation error from pin current variation.

Key Specifications

Pinout & Package

SOT-223 (4-pin) package with exposed thermal tab (pin 2/TAB connected to VOUT). Pin 1 = ADJ/GND, Pin 3 = VIN, Pin 2/TAB = VOUT.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LM1117T-ADJ, TLV1117-ADJ improves dropout by 0.1 V enabling tighter input margins, while LD1117S25TR trades adjustability for enhanced PSRR and extended temperature rating-neither is pin-compatible nor drop-in; both require schematic and layout review.

Availability

LM1117T-ADJ is available at Aetrix Electronics and suitable for post-regulation, battery charging, and portable instrumentation applications requiring stable component supply across industrial temperature grades.

Supply support for LM1117T-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 delivers low-dropout linear regulators optimized for cost-sensitive, thermally constrained applications in industrial, computing, and consumer electronics where simplicity, reliability, and wide input/output flexibility are essential.

FAQ

What is the minimum load current required for stable regulation of the LM1117T-ADJ?

The LM1117T-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 due to internal biasing requirements of the bandgap reference and error amplifier. Below 5 mA, output voltage may rise above the set value, especially at high temperatures or light loads. A small bleeder resistor can be added if system load drops below this threshold.

Can the LM1117T-ADJ be used with ceramic output capacitors?

Yes, the LM1117T-ADJ supports ceramic output capacitors, but requires ≥22 µF capacitance when using them-compared to the 10 µF minimum for tantalum-to ensure phase margin and transient stability. The datasheet specifies an ESR range of 0.3 Ω to 22 Ω; standard X7R ceramics typically fall well within this window. Always verify stability with load-step testing in final layout.

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

The absolute maximum input voltage for the LM1117T-ADJ is 20 V, as specified in the Absolute Maximum Ratings table. However, the recommended operating condition limits input to 15 V to ensure reliable long-term operation and avoid excessive power dissipation. Exceeding 15 V increases thermal stress and reduces lifetime, particularly at high output currents or elevated ambient temperatures.

How does the ADJ pin current affect output voltage accuracy in the LM1117T-ADJ?

The ADJ pin draws 60 µA typical (≤120 µA over temperature), which flows through R1 in the feedback divider. This introduces a current-dependent error: VOUT = 1.25 × (1 + R2/R1) + (I_ADJ × R2). To keep error <1%, select R1 ≤ 124 Ω (e.g., 120 Ω) so that I_ADJ × R2 contributes <12 mV. Higher R1 values increase sensitivity to I_ADJ variation and degrade accuracy.

Does the LM1117T-ADJ include reverse-voltage protection?

No, the LM1117T-ADJ does not include reverse-voltage protection. If VIN is driven below VOUT (e.g., during input short or hot-swap), the internal body diode between VIN and VOUT becomes forward-biased, allowing reverse current flow that can damage upstream sources or cause latch-up. For reverse-polarity or back-drive scenarios, an external Schottky diode from VIN to VOUT (anode to VIN) is required to block reverse current while minimizing forward drop.