The LM317 is an adjustable linear regulator widely used to derive stable output voltages from a higher DC source. It operates by maintaining a constant 1.25V reference between its output and adjust pins, allowing the output voltage to be precisely set using a pair of external resistors.
It is a three-pin, positive-voltage regulator capable of supplying more than 1.5A over an output voltage range of 1.25V to 37V.
The device requires only two external resistors to set the output voltage and offers excellent performance, with typical line regulation of 0.01% and load regulation of 0.1%.




The LM317 is a highly versatile linear regulator that can be used in numerous applications. It can be configured as a standard voltage regulator, a constant current source for battery charging, a tracking pre-regulator circuit, or even an AC voltage regulator circuit.
It also includes built-in current limiting, thermal overload protection, and safe operating area protection, ensuring reliability even under fault conditions. Overload protection remains functional even if the adjust pin is disconnected. Typically, no capacitors are required unless the device is placed far from the input filter capacitors, in which case an input bypass capacitor is recommended. An optional output capacitor can be added to improve transient response, and bypassing the adjust pin further enhances ripple rejection.
For our circuit, we are using the DPAK (TO-252) footprint, which keeps the design compact while still handling decent power. One of the key advantages of this package is the large exposed tab (internally connected to the output), which can be soldered directly onto a wide copper area on the PCB. This effectively turns the PCB itself into a heatsink, helping dissipate the heat generated due to the voltage drop from 12V to 5V. This approach allows for a clean, space-efficient design without needing bulky external heat sinks while still maintaining good thermal performance.
Check out the Datasheet for more info.
https://www.ti.com/lit/ds/symlink/lm317.pdf
PCB DESIGN



We began the project by preparing the schematic for the buck converter board. We did this by studying the LM317 datasheet and creating a simple schematic that included the LM317 setup with two adjustable resistors connected between the adjust pin and the output pin of the LM317. To ensure stability and reduce noise, we added a 10µF SMD capacitor at the input and a 1µF capacitor at the output, which helps smooth fluctuations and improve transient response. We also added extra capacitor footprints at both the input and output in case different-value capacitors are needed later. The output voltage is configured using a resistor divider (330Ω and 1kΩ), which sets the desired voltage reliably.
After finalizing the PCB schematic, we exported the data and converted it into a PCB layout. The PCB editing process began by adding all the components to the PCB design first. We used all SMD components for this project, including 1206 package capacitors, 1206 package resistors, and a DPAK (TO-252) LM317. We prepared a small board of size 20mm x 30mm and placed all the components within this board. We added four CON1 terminals for the VIN, VOUT, and GND pins, placing them along the edges of the board outline. Two CON1 pads were placed on the right side for the input, and two CON1 pads were placed on the left side for the output.
After finishing the placement, we connected all the net lines and completed the board layout.
After finalizing the PCB design, we exported the Gerber files along with the NC drill files and shared them with NextPCB to get the samples manufactured.
NextPCB PCB SERVICE

After completing the PCB design, Gerber data for the PCB was sent to HQ NextPCB, and an order was placed for Blue Solder mask boards with a white silkscreen.
After placing the order, the PCBs were received within a week, and the PCB quality was pretty great.
In addition, I have to bring...
Read more »
Arnov Sharma



ElectronicABC
Alec Probst
hesam.moshiri
Not a buck converter.
Buck converters are high efficiency switching devices that conserve power. An LM317 as used here is a low efficiency linear device that converts excess voltage to heat.