I wanted to learn more about supercapacitor charging.  I had made a few boards using purpose-built ICs, but wanted to make it up of simple blocks that I could tweak and test.  Also, I blew up a few of the purpose-built ICs, and wanted to slow the whole thing down.

First, I designed an ATtiny13A eval board with a 20 MHz external clock.  Then, I designed a "testbed" with the basic parts - input capacitor, half-bridge, inductor, and output current sensor.

I learned a lot, so let me share!