Mini-360 Buck Converter based on MP2307

This is a reverse-engineered component placement diagram from one of the common Mini-360 switch mode power supply circuits. The software to calculate resistor values can be found here and the schematic PDF is here. Essentially, it's the "typical application" copied 1:1 -- I've labled the components as they are in the datasheet, so that it's easy to find your way around there.

Note that there are deliberately underpowered, broken Mini-360 circuits in circulation. These will have horrible efficiency and be a general pain-in-the-butt. Here's what was different in my "broken" version compared to the version I got that was good:

C₁, C₂ is 6.8µF instead of 10µF
L₁ is 2.2 µH instead of 10µH

This will lead to regulator instability and general, horrible performance (40% efficiency and worse). Note that even the ones that are "properly" working have some deficiencies:

C₂ is supposed to be 20µF, but is only 10µF
Bootstrapping capacitor C₅ should be in the range 100nF - 1µF (see datasheet pg. 10) -- only 10nF in circuit
Extenal bootstrapping diode (e.g., 1N4148) is said to improve performance (see datasheet pg. 10) -- not present in circuit
External schottky diode (e.g., MBRS130) is said to improve performance (see datasheet pg. 7) -- not present in circuit

To figure out if you're suffering from regulator instability, the easiest way is to directly measure at the inductor (side facing out). If everything is great, you'll see something like this:

Good module:

If you're experiencing intermittent regulator instabilities, you'll see something like this (if you're lucky):

Intermittent dropouts (too small inductivity or in/out capacitors) -- reduced efficiency:

If it's even worse, you might see something like this:

Intermittent dropouts and ringing (too small inductivity or in/out capacitors) -- drastically reduced efficiency:

Here's the hardware:

Bare PCB:

PCB populated with components:

Component placement: