Revision 5 of SAM D20 Xplained Pro has revision C of the SAMD20J18A device mounted
Known issues
VDDCORE decoupling capacitor
The VDDCCORE output pin on SAMD20J18A has two decoupling capacitors, one 100nF and one 4.7μF. This might lead to a high power consumption when leaving STANDBY sleep mode and the regulator returns to normal operating mode.
Fix/Workaround:
Change the 4.7μF tantalum capacitor (C315) to 1μF ceramic capacitor.