I need to regulate the output from the MCP73871 to 5V and 3.3V. The 5V is to power the digital part of the circuit (microcontroller mostly) and the 3.3V is to power an accurate analog measurement circuit.
The Li-Polymer battery will have a voltage between 2.5 - 4.2 V so must be able to convert from this range to 5V and 3.3V.
I am looking for design recommendations.
Some questions that arises:
1) Is it possible/does it exist a non-switching step-up converter?
2) If I need to use a switching regulator to get 5V, should I use one boost converter to get 5V and one boost/buck to get 3.3V? (As the input voltage might be higher and lower than 3.3V)
3) If I use a switching regulator (boost) to get 5V (for the less sensitive part of the device). Do I still benefit from low noise on the power rails by using a LDO or non-switching regulator to obtain 3.3V if I connect it on the regulator outputting 5V? Is this a better solution with respect to noise on power lines?
4) 5V and 3.3V are very common used voltage levels and I assume there must be some type of chip that can have an input of 2V+ and output both 5V and 3.3V simultaneously? If this is the case, an example of such a chip would be appreciated, but do they have/exist with low noise features?
The questions above reflects my thoughts on how I see this might be solved. Any other ways are very welcome!
I am using an ARM Cortex M-3 running at 72 MHz. It will for the most time be in sleep mode and when running it will be clocked at 72 MHz. Is also has bluetooth communication draining some battery.
It is possible to be running the digital part at 3.3 V as well.