# LM1117 LDO regulator: 800 mA, 1.2 V dropout

> The low-dropout regulator on many 3.3 V boards: versions, dropout, input limit, the output capacitor and the heat it makes.

Canonical: https://roboticsengineering.in/components/lm1117-ldo-regulator/ | Published: 2026-11-03 | Updated: 2026-11-03

**The LM1117 is a low-dropout linear regulator with 800 mA output current and a dropout of 1.2 V at full load, sold in fixed 1.8 V, 2.5 V, 3.3 V and 5 V versions or an adjustable version from 1.25 V to 13.8 V.** The 3.3 V version is the regulator on many ESP32 and Arduino-style boards. Figures are from the Texas Instruments LM1117 datasheet SNOS412Q.

## Key specifications

| Output current | 800 mA |
| --- | --- |
| Dropout | 1.2 V at 800 mA |
| Versions | 1.8, 2.5, 3.3, 5 V, adjustable |
| Input max | 15 V |
| Accuracy | ±1% |
| Protection | current limit, thermal shutdown |

## What the datasheet promises

| Item | Datasheet value |
| --- | --- |
| Output current | 800 mA |
| Dropout voltage | 1.2 V at 800 mA load |
| Versions | 1.8 V, 2.5 V, 3.3 V, 5 V fixed, and adjustable (1.25 V to 13.8 V with two resistors) |
| Maximum input voltage | 15 V |
| Output accuracy | Within ±1 percent (Zener-trimmed band-gap reference) |
| Line regulation | 0.2 percent maximum |
| Load regulation | 0.4 percent maximum |
| Protection | Current limiting and thermal shutdown |
| Output capacitor | A minimum 10 µF tantalum capacitor is required for stability |
| Temperature | 0 °C to +125 °C (LM1117); −40 °C to +125 °C (LM1117I) |
| Packages | SOT-223, TO-220, TO-252, WSON |

The datasheet itself points to the newer TLV1117 as a drop-in alternative, and to the TLV761 for fixed-output SOT-223 designs, so choose by what your board already uses.

## Using it on a robot

- Keep the input between the dropout limit and 15 V. A 2S lithium pack at 8.4 V is fine; a 4S pack at 16.8 V is over the maximum.
- Heat is the voltage drop times the current. Dropping 7.4 V to 3.3 V at 500 mA wastes about 2 W, which needs copper or a heatsink; a buck converter such as the [LM2596](https://roboticsengineering.in/components/lm2596-buck-converter/) wastes much less.
- Fit the required output capacitor close to the pin; a missing or very low-ESR capacitor can make the output oscillate.
- It is a linear part, so for an adjustable rail see also the [LM317](https://roboticsengineering.in/components/lm317-adjustable-regulator/).

## Sources and further reading

- [Texas Instruments LM1117 datasheet (SNOS412Q)](https://www.ti.com/lit/ds/symlink/lm1117.pdf) — every figure in the table above.

Last reviewed: November 2026. The 2 W example is a calculation from the voltage drop and current, not a measurement. No price is quoted because it has not been checked.