2015-02-04 01:37 PM
Hello - I have a few questions on unused pins for this device -
Thank you!
2015-02-04 03:30 PM
We will not use the ADC, DAC, sensors etc. Can we leave VddA open or do we have to supply Vdd power to it? We’re trying to minimize power consumption so if we can leave the ADC, DAC etc. un-powered that would be best.
You need the analogue supply, the power-on-reset circuit uses it, as does the PLL/VCO as I recall. If you don't want the ADC/DAC, don't enable their clocks.2015-02-05 07:41 AM
2015-02-05 08:03 AM
The LSE and HSE are only turned on by user code, the HSE may be enabled by the System Loader with respect to USB/DfuSe
There are a number of pins used at Reset, there are another sub-set used by the System Loader where it is usually looking for transitions on interfaces where ISP connectivity might be coming from. If you are building a board, a complete review of the Data Sheet would be a prerequisite. If I where paranoid I'd have weak pull downs to ground on pins I wasn't using, I would not bond them to ground. Most of the pins default to a Hi-Z input state.