We are currently experiencing an issue with our custom BF524BBCZ-4A based board where VDDRTC or USBVDD both powered by the 3.3V rail develop a short to ground over time. We have 3 prototype boards, the three different shorts are 40, 90 and 400 ohms . I am unable to isolate VDDRTC from USBVDD at the moment so I can't be 100% sure which supply is at fault. Both of the peripherals function fine on these boards but the short causes the hibernate current to be much larger than it should be. A few questions;
1. Is this a known failure mode or something that anybody has seen before?
2. Our board fairly closely follows the BF526-EZBRD and thus does not have any power supply sequencing, the datasheet indicates that this is not an issue?