The **LM317AL-TQ2-R** is a specific variant of the widely-used LM317 family of adjustable positive voltage regulators. It is designed to provide a stable, regulated output voltage that can be set using an external resistor divider. --- ### 1. Technical Specifications The "AL" suffix typically denotes a version with tighter output voltage tolerance or specific thermal characteristics, while "TQ2" refers to the package type. | Parameter | Specification (Typical) | | :--- | :--- | | **Type** | Linear Adjustable Voltage Regulator | | **Output Voltage Range** | 1.25V to 37V | | **Output Current** | Up to 1.5A | | **Input-Output Differential** | 3V to 40V | | **Line Regulation** | 0.01% / V | | **Load Regulation** | 0.1% | | **Operating Temperature** | -40°C to +125°C | --- ### 2. Package and Part Number Breakdown The part number follows a standard industry convention (often associated with UTC - Unisonic Technologies): * **LM317**: Base part family (Adjustable Linear Regulator). * **AL**: High-accuracy version (often ±1.5% reference voltage tolerance). * **TQ2**: **TO-263** package (also known as D2PAK). This is a Surface Mount Device (SMD) designed for high power dissipation. * **R**: Tape and Reel packaging for automated assembly. --- ### 3. Key Electronic Functions The LM317AL operates by maintaining a constant **1.25V reference voltage ($V_{ref}$)** between its Output and Adjustment pins. #### Circuit Configuration To set the voltage, you use two resistors ($R_1$ and $R_2$): ```text Vout = 1.25V * (1 + R2 / R1) + (Iadj * R2) ``` *(Note: $I_{adj}$ is usually negligible at <100µA).* #### Internal Protections * **Current Limiting:** Prevents the device from burning out during an output short circuit. * **Thermal Overload Protection:** Shuts the device down if the internal junction temperature exceeds safety limits (usually 150°C). * **Safe Area Compensation:** Adjusts the current limit based on the voltage differential across the chip. --- ### 4. Application Considerations * **Heat Sinking:** Since this is a linear regulator, excess voltage is dissipated as heat. In the TO-263 (TQ2) package, the large metal tab should be soldered to a copper plane on the PCB to act as a heat sink. * **Capacitance:** * **Input Capacitor:** A 0.1µF disc or 1µF tantalum capacitor is recommended if the device is far from the power supply filter. * **Output Capacitor:** While not strictly required for stability, a 1µF tantalum or 10µF electrolytic capacitor improves transient response.