LM317 DC-DC Step Down Converter Module

The LM317 DC-DC converter is an electronic circuit for converting a DC source voltage from one level to a lower level. This module is important in some portable electronic devices such as cell phones and laptops, which are primarily supplied by power from batteries. The step-down voltage can be easily adjusted and is, therefore, more efficient than using multiple batteries to achieve the same thing.

KEY FEATURES OF LM317 ADJUSTABLE LINEAR REGULATOR MODULE:

• Compact size
• LM317 linear regulator IC with heatsink
• Output voltage adjustment
• Output current up to 1.5A (see chart below)
• Input voltage range 4.5 to 40V
• Output voltage range 1.25 to 37V

Linear regulators have less ripple on their outputs compared to DC-DC converters that can be used for the same purpose, but the trade-off is that the linear regulators also tend to dissipate more heat in the process and so are less efficient than a comparable DC-DC converter.  Linear regulators are best used when the input to output voltage can be kept to a minimum.

The LM317 is perhaps the most commonly used adjustable linear regulator of all time.  It is similar to the ubiquitous 7805 fixed 5V regulator but with an adjustable output that can range from 1.25-37VDC at up to 1.5A.

The LM317 has built-in current limiting and thermal protection features which makes it fairly robust.

The board has 2 holes which can be used for mounting it permanently if desired using two small M3 screws.

Voltage Adjustment

The on-board multi-turn potentiometer allows for adjustment of the output voltage.

The available adjustment range will depend on the input voltage.  The LM317 has a voltage drop of approximately 1.25V, so the typical range is from a minimum of 1.25V up to the input voltage – 1.25V.  If powering the module with 12V for instance, the output range would be approximately 1.25V to 10.75V.

Module Connections

Inputs and output connections on the module are made via small screw terminals that you can connect to using regular hookup wire or the pin on male jumper wires.

The connections are labeled on the back of the board due to the tight component packing on the top.  The ground is common between the input and output terminals (not isolated).

Input Power

• VIN = Input Voltage
• GND = Ground for input

Output Power

• VOUT = Output Voltage
• GND = Ground for output

Note:  Double-check that you have the input and output correctly hooked up before applying power or the module may be damaged.

Technical Specifications