User's Manual

DE910 Series Hardware User Guide
1vv0301183 Rev.1 – 2015-2-13
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Reserved. Page 54 of 70
10.6. VCOIN
The VRTC pin brings out the Real Time Clock supply, which is separate from the rest of the
digital part, allowing only RTC to be active when all the other parts of the device are off. To
this power output a backup capacitor can be added in order to increase the RTC autonomy
during power off of the battery. No devices must be powered from this pin.
For additional details on the Backup solutions please refer to the related application note
(xE910 RTC Backup Application Note).
VRTC also supplies reference power to help DE921 check the time from SMPL (Sudden
Momentary Power Loss).
So it is recommended as best practice to connect VRTC to a shunt capacitor (VRTC to GND)
and the acceptable capacitor value is:
Parameter Min
Keep-alive capacitor
6.8uF
NOTE:
VBATT must be supplied in order to use RTC function.
NOTE:
It is recommended to add a keep-alive capacitor on VRTC.
WARNING:
NO devices must be powered from this pin.