This small module MP1584 buck-converter module seems to be a good solution to power small circuits from higher voltages. Especially cool with this chip is that it accepts input voltages up to 29V. This makes it a perfect candidate for additional circuits that connect to a KNX bus. But it’s not limited to KNX buses. If you want to build a WiFi interface for your Roomba, you also have to down-regulate the 15V battery voltage to 5V or even 3.3V. You want to something to power a circuit from a car battery? This seems to be a perfect circuit for there use cases.
With it’s tiny dimensions of 17 x 22mm it’s size is around the size of 2 MicroSD cards (and much smaller than a single SD card).
The output voltage of the module is controlled by a tiny potentiometer. You will need a multimeter to check the output voltage before connecting it to a circuit.
While the plain voltage range data seems to be quite good, how does the circuit behave on different loads? Some Chinese dealers claim that similar modules should handle 3A load. If you just look at the size of the inductor you might already start thinking that this most likely isn’t true. However, DC resistance of the inductor is approximately 10mOhm (I miss my Kelvin probes and therefore could only measure this very roughly).
Let’s start with 29V input voltage – this will bring everything to the limit. Output voltage is fixed to 5V in this experiment. Without any current drawn, it still looks a bit rough:
However, a voltage swing of (Vpp) 98mV is no problem at all. Between 0.1A and 0.9A the circuit behaves quite well. Vpp is around 0.2V (a bit lower on low currents, higher in higher currents)
We reach the end at 1A. Now the regulator doesn’t provide a stable output voltage anymore:
But what about lower input voltages? Let’s go the the other “extreme”: 9V (it will work with even less, but let’s give it a bit headroom).
Almost perfectly clean with no load:
A bit more stable than at 29V for currents between 0.1A and 0.7A:
And at 0.7A we reach the end of the useable current range:
Conclusion: This module works fine for almost every embedded use case: Arduino, ESP8266 WiFi modules and even a Raspberry Pi without any additional USB devices plugged in.
Here are 2 animation that shows the output voltage under different loads:
29V input, 5V output, 0-1A in 0.1A steps:
9V input, %V output, 0-0.7A in 0.1A steps: