AMS1117 Adjustable Voltage Regulator IC

The AMS1117 Adjustable Voltage Regulator is a reliable, low-dropout (LDO) linear regulator designed to provide a stable, adjustable output voltage for a wide range of electronics components and modules. Ideal for both Arduino and Raspberry Pi projects, as well as professional designs, it ensures clean power rails for microcontrollers, sensors, and mixed-signal circuits.

⚙️ Key Features

• Adjustable output voltage: Precisely set the output to your target voltage using an external resistor divider.
• Low dropout voltage (LDO): Efficient operation even when VIN is close to VOUT, reducing wasted power.
• High accuracy: Stable regulation for dependable performance in digital and analog applications.
• Thermal overload protection: Automatically limits operation under excessive temperature to protect the device.
• Short-circuit current limiting: Safeguards the regulator and load from fault conditions.

📐 Technical Specifications

• Output Voltage: Adjustable (set via external resistors; typical reference ≈ 1.25 V)
• Dropout Voltage: Low (typ. around 1.1 V at high load; ensure sufficient headroom)
• Accuracy: High (tight reference and regulation for steady output)
• Protection: Integrated thermal overload and short-circuit limiting
• Output Current: Up to approximately 1 A (thermal and dropout dependent)
• Recommended capacitors: Input ≥ 10 µF and output ≥ 10 µF placed close to the pins (low-ESR types recommended)
• Typical package: SOT-223/DPAK style (varies by supplier)
• Pinout (SOT-223): 1 = ADJ/GND, 2 = VOUT, 3 = VIN; tab/heatsink is tied to VOUT

Note: Exact electrical limits and tolerances can vary by manufacturer. Always consult the specific AMS1117-ADJ datasheet for your device.

🧮 Setting the Output Voltage

The adjustable version uses two resistors: R1 from VOUT to ADJ, and R2 from ADJ to GND. The output is approximately:
VOUT ≈ 1.25 V × (1 + R1/R2) + IADJ × R1 (IADJ is small and often neglected for practical designs)

• Common starting point: R2 ≈ 240 Ω, then choose R1 to achieve your target voltage.
• Place the divider close to the IC and route grounds carefully for best regulation.

🔌 Application Examples

• Power supply design: Create stable rails for Arduino shields, Raspberry Pi peripherals, and microcontroller boards.
• Post-regulation: Clean up noisy supplies for analog circuits, ADC/DAC, and RF modules.
• Logic level rails: Step 5 V down to 3.3 V for sensors and wireless modules (e.g., ESP8266/ESP32), observing dropout and thermal limits.
• Local regulation: Point-of-load regulation for distributed systems and electronics components on mixed-signal PCBs.
• Energy management: Efficient linear regulation where simplicity and low noise are preferred over switching solutions.

🛠️ Design Notes & Best Practices

• Headroom: Ensure VIN ≥ VOUT + dropout (allow ~1.2–1.3 V margin at higher currents).
• Thermal management: Power dissipation P = (VIN − VOUT) × IOUT. Use copper pour on the tab (VOUT) for heatsinking.
• Stability: Use recommended input/output capacitors close to the pins; keep traces short to minimize impedance.
• Protection: Built-in thermal shutdown and short-circuit limiting enhance robustness under fault conditions.

🤝 Ideal For Makers and Engineers

Whether you are prototyping on a breadboard with Arduino, integrating peripherals with Raspberry Pi, or designing production hardware, the AMS1117-ADJ offers a dependable, low-noise power solution for your electronics modules and microcontroller-based systems.