I am designing a PCB around the SAM D21 (with Arduino bootloader) and had some general optimization questions. The first question is the most important to answer in my application.
- I currently have a 3.3V buck DC-DC switching regulator (Max1921) in preceeding an LDO in order to regulate my USB and battery inputs down to 3.3V. I am using the buck regulator as it reduces power consumption and the LDO as it results in a low noise output. The LDO is used to regulate the output of the buck regulator. Is this overkill?
2 I am using a MBR120 schotky diode in order to be able to switch between USB and battery power. However, I have noticed that this diode has a forward voltage of almost 0.4V resulting in a significant battery voltage drop into the regulator and less battery time. Is there a better alternative to using the diode with the same functionality?
- Finally, I am using a voltage divider configuration (2 100k resistors) in order to monitor my battery and USB input (I can determine whether battery or usb is plugged in). However, these resistors slightly waste some current. Is there a power efficient method of measuring my battery voltage?
Thanks for all your help!