User's Guide

xE922-3GR Hardware User Guide
1VV0301272 Rev.0.8 2017-01-05
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Reserved. Page 48 of 112
The following table gives an overview of V_RTC minimum voltage level requirements in order to keep RTC
running:
condition
minimum V_RTC [V]
min Typ max
room temp
erature
0.8
1.1
-40 to +125deg
0.9
1.2
So typically at room temperature a voltage difference of 2.3V – 0.8V = 1.5V is available for buffering the
RTC supply in case V_BAT is removed.
An external capacitor for RTC buffering can be added, typical 100uF, up to maximum 220uF directly to the
LGA pin V_RTC.
In case an extreme large (super) capacitor, typical 1 F, is applied, a series resistor of typical 470 Ohm should
be added.
Typical current drawn from V_RTC by the RTC clock: 2.6µA
An RTC alarm is one of the possible events to power ON the module.