Overview
The LM1117 is a low-dropout linear voltage regulator capable of providing a stable output voltage with a maximum output current of 800 mA. It is designed for applications requiring a low dropout voltage and precise output voltage regulation.
Key Features
- Low Dropout Voltage: The LM1117 has a dropout voltage of 1.2V at 800 mA of load current.
- Output Voltage Options: Available in both fixed and adjustable versions. Fixed output voltages include 1.8V, 2.5V, 3.3V, and 5V. The adjustable version can set the output voltage from 1.25V to 13.8V using two external resistors.
- Thermal and Current Protection: Includes built-in thermal shutdown and current limiting to protect the regulator and the load.
- Accuracy: The output voltage accuracy is within ±1% due to a Zener-trimmed band-gap reference.
Applications
- The LM1117 is commonly used in:
- Battery Chargers
- PCs and Consumer Electronics
- Industrial AC/DC Modules
- Servo Drive Control Modules
- Ultrasound Scanners
Pin Configuration
- The LM1117 typically has three pins:
- ADJ/Ground: Connects to ground in fixed voltage mode or acts as an adjust pin in adjustable mode.
- Output: Provides the regulated output voltage.
- Input: Receives the input voltage.
Electrical Characteristics
- Input Voltage Range: Up to 20V.
- Output Current: Up to 800 mA.
- Line Regulation: 0.2% (maximum).
- Load Regulation: 0.4% (maximum).
- Operating Temperature Range: 0°C to +125°C for LM1117, -40°C to +125°C for LM1117I.
Example Circuits
Fixed Output Voltage
- To obtain a fixed output voltage, capacitors are used at the input and output to filter noise and stabilize the voltage. A minimum of 10µF tantalum capacitor is required at the output to improve transient response and stability.
Adjustable Output Voltage
- For adjustable output, the LM1117 uses a reference voltage of 1.25V across a resistor to set the desired output voltage. The output voltage can be adjusted using two external resistors according to the formula: $ V{OUT} = V{REF} left(1 + frac{R2}{R1}right) + I{ADJ} cdot R2 $ where ( V{REF} ) is 1.25V, ( R1 ) and ( R2 ) are external resistors, and ( I_{ADJ} ) is the adjustment pin current.
Package Information
- The LM1117 is available in various packages, including SOT-223, TO-220, TO-252, WSON, and TO-263.
Summary
The LM1117 is a versatile and reliable voltage regulator suitable for a wide range of applications, offering both fixed and adjustable output voltages, low dropout voltage, and robust protection features.