12Vdc 3A Adjustable Regulator Power Supply Circuit with LM317The LM317

The LM317 is an adjustable, positive 3-terminal voltage regulator capable of supplying 100 mA (for RA87U control) or 1.5 A (for Order Code UF27E and N61CA) across an output voltage range of 1.2 V to 37 V. These voltage regulators are notably user-friendly, requiring only two external resistors for output voltage setting. Both line and load regulation performance surpasses that of standard regulators. Comprehensive protection against overload is provided through on-chip current limiting, thermal protection, and a safe operating area. The device remains fully operational even if the adjustment terminal is disconnected, ensuring reliable performance without failure. Order UF27E is packaged in a TO-220 style, Order RA87U in a TO-92 style, and Order N61CA in a TO-263 style.

The LM317 voltage regulator is designed to deliver a stable output voltage that can be adjusted based on the requirements of the application. Its adjustable output voltage feature is achieved through a simple resistor divider network connected to the adjustment terminal. The output voltage can be calculated using the formula: Vout = Vref (1 + R2/R1) + Iadj * R2, where Vref is typically 1.25 V, R1 is the resistor connected from the output to the adjustment terminal, and R2 is the resistor connected from the adjustment terminal to ground.

The device's ability to provide a maximum output current of 1.5 A makes it suitable for a variety of applications, including power supplies for microcontrollers, sensors, and other electronic components that require a stable voltage source. The LM317's internal circuitry ensures excellent load regulation, minimizing the impact of variations in input voltage or load current on the output voltage.

Thermal protection is a critical feature of the LM317, preventing damage due to overheating by shutting down the output when the junction temperature exceeds safe limits. The on-chip current limiting feature further protects the device and connected components from excessive current conditions.

The LM317 is available in multiple package styles, allowing for flexibility in design and integration into various circuit layouts. The TO-220 package is ideal for applications requiring heat dissipation, while the TO-92 and TO-263 packages are suitable for more compact designs. This versatility, combined with its robust protection features and ease of use, makes the LM317 a popular choice among engineers and designers in the field of electronics.The LM317 is to provide an adjustable, positive 3-Terminal Voltage Regulator 100mA (RA87U control) or 1. 5 A (Order Code UF27E and N61CA) over a range of output voltage of 1. 2V to 37V. These voltage regulators are exceptionally easy to use and requires only 2 reistors external output set.

Both line and load regulation are better established than st andard regulators. Protection against overload is fully furnished with on-chip current limiting, thermal protection and safe area. This will remain fully functional even if the adjustment terminal is disconnected, making it virtually blow-out.

Order UF27E comes in a TO-220-bag style. Order RA87U comes in a TO-92-style bag. Order N61CA comes in a TO-263-bag style. 🔗 External reference