Posted on February 29, 2016 at 17:31The capacitor and resistor values would depend on the characteristics of your chosen crystal. I would check the manufacturer's specifications, and part numbering schemes, to get a starting point there. There maximum frequency of the STM32F0 is going to be dependent on the speed of the transistors due to the CMOS process window, voltage, temperature and critical paths in the design. The flash array is likely to be a big contributor here, as it is large and slow. The 32-bit timers in the peripheral realm.
What does the data sheet indicate? There is usually a table of voltage, speed, and flash wait states. Look also at the L0 parts, these are apt to be viable at lower voltages.
The use of USB is also predicated on sufficient voltages for the pin drivers to meet specifications.
