In Idle Sleep mode the AC will continue to operate as normal.
In Standby Sleep mode the AC is disabled by default. If the Run in Standby
Sleep Mode bit (RUNSTDBY) in the Control A register (ACn.CTRLA) is written to
'1', the AC will continue to operate as normal with event, interrupt
and AC output on pad even if the CLK_PER is not running in Standby Sleep mode.
In Power-Down Sleep mode the AC and the output to the pad are disabled.