Overview: LM317 Adjustable Voltage RegulatorThe LM317 is a widely used adjustable linear voltage regulator IC designed for DC-DC applications that require precise and reliable voltage control. It provides an adjustable output range from 1.25V to 37V and can deliver up to 1.5A of output current with built-in current limiting, thermal overload protection, and safe-area compensation for dependable operation in DIY and professional circuits.Key FeaturesAdjustable output voltage: 1.25V to 37VOutput current up to 1.5ABuilt-in current limiting and thermal protectionHigh regulation and stability under varying loadsSimple resistor-set voltage adjustmentTO-220 package for easy mounting and heat-sinkingSpecificationsReference voltage (Vref): 1.25V (typical)Output voltage range: 1.25V to 37VMaximum output current: 1.5ATypical dropout voltage: around 2-3V (depends on load)Adjust pin current (Iadj): typically ~50 microampsPackage type: TO-220Voltage Setting FormulaSet the output voltage using two resistors (R1 and R2) with the following formula:Vout = Vref * (1 R2 / R1) Iadj * R2, where Vref ≈ 1.25V.Common example: using R1 = 240 ohms gives Vout ≈ 1.25 * (1 R2 / 240).Typical ApplicationsDIY regulated power suppliesBattery charging circuitsMotor speed control and small motor driversLED drivers and constant-current applications (with appropriate resistor or current-limiting circuitry)General-purpose voltage regulation for test rigs and prototypesTypical Circuit and Usage TipsProvide adequate input-to-output headroom. The input voltage should be at least 2-3V higher than the required output to account for dropout.Use a heatsink for sustained currents near the 1.5A limit to avoid thermal shutdown.Place an input bypass capacitor (0.1uF) close to the regulator input and an output capacitor (1uF or larger) for stability, especially when the regulator is located far from the supply source.Consider a bypass capacitor between Adj and ground (e.g., 10uF) to improve ripple rejection when needed.Follow safe wiring practices and observe polarity to prevent damage.Package and PinoutPackage: TO-220. Pinout (front view, left to right): Adj, Output, Input. The metal tab is connected to the output and can be bolted to a heatsink for improved thermal performance.Safety and HandlingInternal thermal limiting and current limiting help protect the device, but proper heatsinking and current control are required for reliable continuous operation.Avoid exceeding the maximum input voltage and the device power dissipation ratings.Use appropriate fusing or current protection when designing battery chargers or high-current circuits.NotesImages are for illustration purposes only. Category: Buck, Boost Converters and Regulators Tags: Adjustable Voltage Regulator, DC regulator, Electronics Components, LM317, LM317 adjustable regulator, LM317 DC-DC, LM317 power supply, LM317 TO-220, LM317 voltage regulator, voltage regulator IC College Road Electronics4.85 (317 Reviews)
