Step-up converter with current feedback measurement.

CPU: ATtiny45
Driven by PWM output OC1B (PB4 pin) with MOSFET.
Current feedback measured at ADC3 (PB3 pin).
Output on the PB4 header (pin 1 is negative, pin 2 is positive side).


Bill of materials:

C1,C2	1.5uF tantalum
C3,C51	10uF ceramic
D50	SS24 Schottky diode (SMB package, 40V, 2A)
L50	470uH, 390mA, 200 mil pin distance (probably too big for 20mA LEDs :-)
PB4	two-pin header soldered to pins 1 and 2 of PB4
Q50	IRLML6344TRPBF N-channel MOSFET, 30V, 5A, SOT-23 package
R40	220nF capacitor (not resistor!)
R45	1K5
R50	15K
R51,R53	0R00 (zero-ohm link)
R55	1R0 (can safely measure currents from ~8 mA up, for smaller currents use higher value)
U1	ATtiny45-20SU
U2	MCP1703T-5V


Firmware:

The firmware is a dumbed-down version of firmware for my other
project: http://www.fi.muni.cz/~kas/bike-lights/, modified
for ATtiny45.