AMS1117 3.3V 1A Low Dropout (LDO) Voltage Regulator (SOT-223)

If you look closely at an Arduino Uno, NodeMCU, or ESP32 dev board, you will almost always find an AMS1117 soldered right near the USB port or power jack. It is the absolute industry standard for on-board voltage regulation.

Unlike a massive LM2596 buck converter module, the AMS1117 is a discrete Low Dropout (LDO) linear regulator packaged in a tiny SOT-223 footprint. "Low Dropout" means it can regulate a clean 3.3V even if the input voltage is only slightly higher (e.g., 4.5V or 5V). Standard regulators (like the older 7805) require at least a 2V difference to work properly.

Whether you are designing a custom ESP32 buffer board for your Thinking Robot kits or just need a quick way to power a 3.3V sensor from a 5V rail, this IC is mandatory. It features built-in current limiting and thermal shutdown, meaning it will protect itself (and your expensive sensors) if it gets too hot or accidentally shorts out.

Hardware Design Tip: To ensure a stable output and prevent voltage oscillation, always place a 10µF to 22µF capacitor between the Output pin and Ground, as well as another on the Input pin.

Key Features

• Output Voltage: Available in fixed 3.3V, 5.0V, or Adjustable (ADJ) versions.
• Max Output Current: Up to 1A (Crucial for power-hungry Wi-Fi chips like the ESP8266 or ESP32).
• Low Dropout Voltage: Typically 1.1V to 1.3V at maximum load.
• Input Voltage: Up to 15V maximum (Recommended: 4.5V to 12V).
• Package: SOT-223 (Surface Mount — but large enough to easily solder by hand).
• Protection: Built-in thermal shutdown (150°C) and current limiting.

Pinout Guide (SOT-223)

1. Pin 1 (GND / ADJ): Common Ground (for fixed versions like the 3.3V) or Adjust (for variable versions).
2. Pin 2 (VOUT): Regulated Output Voltage (e.g., exactly 3.3V). Note: The large metal tab on the top of the chip is also internally connected to VOUT to act as a heatsink.
3. Pin 3 (VIN): Unregulated Input Voltage (e.g., 5V from a USB line or battery).