Sometimes I need a 3.3V power source but the only one that I have are the 1.2 volt rechargeable or the common 1.5V alkaline batteries therefore I’ve searched for some type of DC to DC boost converter that will step-up the 1.5V voltage to the 3.3V that is required for my project.
After seaching the www I’ve found 2 ICs that are still available on the market, have a low price and do not need a lot of external components. One of it is the MCP1640 produced by Microchip and the typical circuit schematic if presented below:
The VFB pin is used to provide output voltage regulation by using a resistor divider. Feedback voltage will be 1.21V typical with the output voltage in regulation. The maximum output current is 150mA.
The second circuit is built with LTC3400 IC produced by Linear Technology and the schematic is almost the same as the one with the MCP1640 IC:
The output voltage can be adjusted to 3.3V (from 2.5V to 5V) by using this formula:
VOUT = 1.23V * [1 + (R1/R2)]
You need to connect the SHDN pin to Vin through a 1MΩ pull-up resistor. The maximum output current is 100mA.
As you can see is pretty simple to have a 3.3-Volt power source that cost around $2 if you use the MCP1640 IC or $6 with the LTC3400 IC.