Bear in mind, I have zero electrical background, this is just a hobby so correct me if I make mistakes. This question is part of my journey trying to create my own pcb.
I want to create a power supply for an ATmega328P SMD microcontroller and a Legacy Digi XBee S1. According to the datasheets the XBee operates between 2,8-3,4V and the ATmega328P operates between 1,8-5,5V. Together I expect them to draw less then 150mA in power.
I decided to use 2 Li-ion cells to supply the power (they supply 3,7V in parallel). Now to make sure the voltage stays within range for both devices I decided to put a voltage regulator in my circuit.
I chose the TPS78001DDCR SOT because this voltage regulator uses very little power by itself and from what I've read should be one of the most efficient ones.. (long battery life is important to my application).
The datasheet mentions (as seen in the images) that it's a good idea to add capacitors to the IN and OUT pins. I have selected KEMET C0603C105K9RACTU as the to be used capacitors with a value of 1µF.
I have schematics and a custom parts library in Eagle for all of this. This is an edited diagram after remarks from Bimpelrekkie:
My question is:
- Am I right that the chosen voltage regulator is the better choice for my application (terms of efficiency)?
- Did I choose the right capacitors (1µF)? The datasheet mentions 0.1µF aswell.
- How do I program the output voltage (3.3V)? I can't seem to wrap my head around the calculations done for programming the regulator. (datasheet chapter 7.5 or page 17)
Thank you for reading this far :)