AMS1117-3.3 LDO Voltage Regulator (1 A, SOT-223)

Fixed 3.3 V LDO Voltage Regulator

The AMS1117-3.3 is a low-dropout (LDO) linear regulator delivering a fixed 3.3 V output at up to 1 A continuous current. Housed in a SOT-223 package with an exposed thermal tab, it is one of the most popular 3.3 V regulators in hobby, maker, and commercial embedded designs.

Pin Configuration

• Pin 1: GND (ground; the metal tab is internally tied to GND)
• Pin 2: Vout (3.3 V regulated output; requires 22 uF tantalum Cout minimum for stability)
• Pin 3: Vin (input voltage; max 15 V, recommended 4.75-12 V; requires 10 uF Cin minimum)

Key Specifications

• Output voltage: 3.3 V +/- 1%
• Output current: 1 A continuous
• Dropout voltage: 1.2 V max @ 1 A
• Quiescent current: 5 mA typical (no load)
• Line regulation: 0.2% max (Vin 4.75-12 V)
• Load regulation: 0.4% max (10 mA to 1 A)
• Ripple rejection: 60 dB @ 120 Hz
• Operating junction temperature: -40 to +125 C
• Package: SOT-223 (6.5 x 7.0 mm incl. leads), RoHS compliant

Typical Application

• 3.3 V rail for ESP32, STM32, RP2040, and other MCU boards
• Power supply for sensors and 3.3 V logic peripherals
• Battery-powered IoT nodes (drop-out from a 5 V or 12 V source)
• Reference voltage for ADCs and DACs
• Drop-in replacement for LM1117-3.3 / LD1117S33

Required External Components

• Cin: 10 uF min tantalum or low-ESR electrolytic on Pin 3 (improves transient response and ripple rejection)
• Cout: 22 uF min tantalum (10 uF min acceptable for ceramic) on Pin 2 (required for stability)

Thermal and PCB Layout Notes

The SOT-223 thermal tab is internally tied to GND. Solder the tab to a copper pour (at least 100 mm squared) on the PCB for heatsinking. Maximum power dissipation is 1.2 W at 25 C with no heatsink, falling to ~0.6 W at 85 C ambient. The chip includes internal thermal shutdown and short-circuit protection with auto-recovery.

Package Contents

• 1 x AMS1117-3.3 LDO regulator in SOT-223 package (tape-and-reel cut strip)