The voltages of Li batteries are between 3.6 and 4.2 Volt. When the 3.3Volt microchips are used, a simple low drop voltage regulator LP2950-3.3 can be used, if the Li battery voltage is at least 3.8 Volt.
There is a very interesting alternative. The DC-DC convertor PTN0405C from Texas Instruments changes an input voltage from 2.95 to 5.5 Volt into an output voltage of 5-15Volt, just by changing one resistor. No coil is needed, only 2 capacitors. Using a Li-battery in connection with this converter, it is possible to use the regular 5 Volt microchips. In this case, even the resistor is not needed.
- 6W and 12W converter are available
- PTN0405C_scheme.jpg (25.27 KiB) Viewed 12893 times
- Easy to handle PCB
- PTN0405_board.jpg (7.92 KiB) Viewed 12893 times
Jan Lichtenbelt
Datasheet: See Farnell http://www.farnell.com/ and search for PTN0405