XL4015 Adjustable DC-DC Step-Down Module with Display

Description

The XL4015 Adjustable DC-DC Step-Down Module can can step-down the input voltage to a range of 1.25 – 35V at up to 4.5A.

PACKAGE INCLUDES:

• XL4015 Adjustable DC-DC Step Down Module
• 4 standoffs and hardware
• Heatsink

KEY FEATURES OF XL4015 ADJUSTABLE DC-DC STEP DOWN MODULE

• XL4015 step-down converter IC
• Output voltage adjustment
• Built-in red voltmeter shows input and output voltage
• Output current up to 4.5A (see chart below)
• Input voltage range 4.5 to 38V
• Output voltage range 1.25 to 35V

DC-DC Step-Down converters (also known as ‘Buck’ converters) convert a higher voltage to a lower voltage while also stepping up the available current.

This DC-DC Step-Down converter is adjustable and capable of outputting a voltage in the range of 1.25 to 35V at a continuous current of up to 4A and short-term current of up to 4.5A with a maximum power output of up to 75W.  The input voltage must be higher than the output voltage.

The XL4015 converter IC has over current limiting and thermal shutdown features built-in.

There is an on-board green LED that illuminates when power is applied.

The module ships with a small heatsink that has adhesive pre-applied.  The heatsink can be attached to the XL4015 converter IC to help keep it cool.

The board has 4 holes in the corners which can be used for mounting it permanently if desired using  small screws.  The module comes with 4 standoffs that can be installed into these holes to space the module up if desired for benchwork.

Output Display

The built-in red voltmeter display shows the input and output voltage.

There are 2 buttons which control the display. The button on the left (near the Vin- terminal) turns the display on or off. The button on the right switches the display between displaying the input voltage and displaying the output voltage. There are two red LEDs marked ‘IN‘ and ‘OUT‘ that indicate which voltage is currently being displayed.

The display has a stated accuracy of ± 0.1V.  Some versions of the module have a calibration sequence that can be performed to calibrate the display against a reference voltmeter if desired.

To calibrate the display, perform the following steps:

1. select the voltage reading (input or output) that you want to calibrate so that it is shown on the display.
2. Hold the right button down for approximately 2 seconds. When you release it, the display should be blinking which indicates that it is in the calibration mode.  If the display is not blinking, then it is a version of the module that does not support the calibration process.
3. Use the left button to decrement the reading down and the right button to increment it up. Each press of the button adjusts the calibration by less than 0.1V, so you may need to press the button several times to see a change in the reading.
4. Once you are happy with the reading, press the right button again for approximately 2 seconds to save the setting.

Voltage Adjustment

The module has a multi-turn potentiometer for adjustment of the output voltage.

Turning the pot CW increases the output voltage while turning it  CCW decreases the output voltage.

The lowest output voltage is approximately 1.25V.  The upper limit of the adjustment range will depend on the input voltage and is typically about 1.5V less than the input voltage.  With a 12V input for instance, the upper output limit will be approximately 10.5V.

Input Power

These are compact boards with input power applied to one end and output power available on the other end.

With the LED display facing towards you, the input is on the left and the output is on the right.  The connections are made using screw terminals for easy connection to wires for hookup.

The input has a reverse polarity protection diode.

Input Power Terminals (Left Side)

• IN+ = Input voltage (4.5 to 38V)
• IN- = Ground

Output Power

Output power is available on the right side of the module.  It also uses screw terminals for easy connection to wire for hookup.

Output Power Terminals (Right Side)

• OUT+ = Output voltage (1.25 to 35V)
• OUT- = Ground

OUR EVALUATION RESULTS:

You can find variations of these DC-DC converters for sale in many places were you will find them rated at up to 5A, but we feel they need to be derated based on the construction of the module.  Though these units do have a nice beefy inductor some of the other components fall a little short.

Output filter cap:  The output filter cap is rated for 35V which limits the max voltage output slightly, so we derate it slightly to 35V on the output

Heat sink:  The modules come with a heat sink that can be applied to the XL4015 converter IC.  The supplied heat sink is either small or almost too large to fit and in either case it has to be applied to the plastic body of the device since the thermal tab is soldered to the board, so it is not very effective in removing heat even when forced air is applied.

Built-in XL4015 protections:  The XL4015 converter IC has built-in thermal shutdown and current limiting, but we found that if an excessive load beyond its specs it applied suddenly, the chip can fail before a safe shutdown can occur. If you are trying to find the max output of this module, it is best to load it gradually to avoid possible permanent damage.

Voltmeter:  The voltmeter is operated off a small LM317 linear voltage regulator.  When the module is operated near its thermal limits, especially with high input voltages, the LM317 may overheat and thermally shutdown and the voltmeter display will go blank.  The DC-DC converter module will remain operational and the display will return once the module thermals are reduced.  Think of it as feature.  It gives you a visual warning that you are getting close to the thermal limit of the module.

Despite the issues noted here, the modules do have a good price/performance ratio if they are used within their limits as outlined here.  If you want something that can easily handle 3A over its range, this is a good choice to consider.

The table below gives some thermal results with an ambient temp of approx 25°C and the module operating at different input and output voltages and current loads set at 3A, 4A and/or the max amperage without kicking in thermal shutdown.

Power dissipation changes significantly depending on input and output voltages, so refer to the table for expected performance in your target application.

As a general guideline, for typical input/output operating voltages, at 3A the module is operating within its comfort range.  At 4A is it starting to get pretty warm but running OK with a few exceptions where it is getting pretty hot.  4.5A is the upper max current that we found. For long-term operation, it is recommended to not run the converter IC over about 80C.  For short-term prototype use, temps up to low 90’s are acceptable.

Output Current vs Input / Output Voltage

The ripple and noise on the output is typically around 50-200mv peak-peak depending on settings and load which is pretty good and should be fine for most applications.

The scope capture below shows the typical ripple/noise found on the output.

XL4015 Ripple and Noise