4.1.4.3 Backup Area/Supply Controller Pins

In all power supply figures shown above, FWUP, SHDN, WKUP/TMP[2:0] and RTCOUT0 are input/output pads referenced to the output of the power switch. As a result, the logic levels of the corresponding pins shift up or down depending on the voltage level of VBAT and VDD3V3 to which the power switch is connected. If more generic wake-up pins other than WKUP[2..0]/TMP[2..0] are needed as wake-up sources from Backup mode, or as anti-tamper inputs, VDD3V3 must be present in Backup mode.