5.3.5 Backup Super Capacitor

SAM E54 Xplained Pro has a 47 mF backup super capacitor for use with the SAM E54 backup system. The super capacitor can be connected to the device as described in VBAT Backup Select.

Due to the high capacitive load represented by the super capacitor, a 220Ω limiting resistor is added to reduce inrush current. The source for charging is the targets main supply and a low-power opamp is used for disconnecting the charger input when removing power. This is added to avoid a current leak back to the main supply from the super capacitor when power is removed.

A full charge of the super capacitor from an empty state will take approximately 45 seconds and can supply the target device in backup mode with ULP running for up to ~20 hours. Other modes are not characterized, but will reduce the available time in backup mode respectively. For more information about the current consumption in other modes, refer to the electrical characteristics chapter in the SAM E54 datasheet.

CAUTION: Due to an issue with the VBAT pin in the A0 revision of ATSAME54P20A there is an over-consumption of current in the VBAT pin when VBAT > VDDIO. This issue renders the on-board super capacitor backup solution not usable.