AMS1117 3.3V LDO Regulator
Fixed 3.3V linear regulator for powering logic-level components.
Wiring & code for
AMS1117 33 practical reference
A simple fixed 3.3V linear regulator found on countless breakout boards to safely power 3.3V logic from a 5V source. The AMS1117-3.3 takes an input voltage a bit above 3.3V and drops it down to a clean, stable 3.3V output using simple linear regulation — no switching, no configuration, just a dropout voltage and some wasted heat — making it the near-ubiquitous small regulator seen on the back of ESP8266, ESP32, and countless sensor breakout boards whenever 3.3V logic needs to be derived from a 5V supply.
Key specifications
- Regulator type: AMS1117-3.3 fixed 3.3V low-dropout (LDO) linear voltage regulator
- Input voltage: 4.75V–15V DC (practical range; must exceed 3.3V output by the dropout voltage)
- Output voltage: Fixed 3.3V DC (non-adjustable — the '-3.3' in the part number denotes this fixed version)
- Dropout voltage: ~1.1-1.3V typical at full rated current
- Output current: Up to ~1A (with adequate heatsinking/cooling; less at higher input-output voltage differential due to heat dissipation)
- Package: Commonly SOT-223 surface-mount package on breakout boards, sometimes TO-220 for higher-current bare regulator boards
- Efficiency: Lower than a switching (buck) regulator — wastes power as heat proportional to the input/output voltage difference and current drawn
Pinout and connection notes
Being a linear regulator, the AMS1117-3.3 dissipates the input-to-output voltage difference as heat proportional to the current drawn — fine for small logic loads (tens to a few hundred mA) but it will run noticeably warm and waste real power if pushed near its 1A rating from a much-higher-than-3.3V input; for higher-current or higher-efficiency 3.3V generation, a switching buck regulator is a better choice.
- VIN: Regulator input, 4.75-15V DC
- GND: Ground (also the regulator's tab/heatsink connection on some packages)
- VOUT: Regulated 3.3V DC output
Integration checklist
- Confirm the exact part number and breakout-board revision.
- Verify supply voltage, current demand, logic levels, and signal direction against the datasheet.
- Check controller pin assignments and bus address or interface mode against the example code.
- Power up with external loads disconnected, then test signals before full integration.
- If readings or communication fail, check power and ground first, then pin mapping, interface settings, and library initialization.
Troubleshooting and reproducibility
Record the board used, wiring, library/version, supply arrangement, and measured behavior. Use the selected board-specific wiring example as the source of truth. Never assume visually similar modules share identical voltage tolerance or pin order.