/diy/ - Do It Yourself

>>1274566
What are your other constraints? Max current, packaging, inductor physical size? If you're just powering the micro and not sourcing any significant I/O current, only sinking, a micropower LDO linear regulator with a low quiescent current wouldn't kill you as far as power waste. LP2950/LP2951 might be good choices here.
The MC34063 is cheap and available, but its max switching frequency is 100kHz, which requires a larger inductor. PDIP available.
XL4005 outputs 5A and runs at a slightly higher 300kHz so slightly smaller inductor, but TO263-5L SMD package and 3-5mA quiescent current.
TPS54232 is good for adjustable output voltages at 2A, 28V max input, runs at 1MHz so you can use a very small inductor. Good quiescent current. SO-8 package.
Most of the bucks in SOT23-size packages are well-behaved, high-frequency, efficient, and easy to design-in. Some are even synchronous, i.e. instead of an external Schottky or FR they have an active switch inside the package, which is extra efficient and convenient.
>P-fet driver
As has happened at least once here on /ohm/, the absolute wrong circuit for some other job is a great fit for the next one. The ill-fated motor driver circuit of >>1273279 is a great, simple gate drive circuit. Here I use it to provide current amplification for a resistive voltage divider. If resistors are more convenient to hand than transistors, you can replace either of the transistors with a fixed resistor, with an increase in turn-on time. This driver won't work well with FETs with low Vgs(on).

>>1274610
18nF gate capacitance sucks