GE864-AUTO Hardware User Guide
1vv0300779 Rev.0 - 20/06/08
Reproduction forbidden without Telit Communications S.p.A. written authorization - All Rights Reserved
page 49 of 62
10.9 RTC Bypass out
The VRTC pin brings out the Real Time Clock supply, which is separate from the rest of the digital
part, allowing having only RTC going on 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.
10.10
External 32KHz oscillator
The GE864-AUTO has an internal 32.768 KHz oscillator for ‘power saving’ and ‘Real Time Clock’
features.
A common 32.768 KHz crystal is not reliable for ‘automotive’ applications.
For this reason, the
GE864 AUTO
will not have an internal oscillator, but the 32.768 KHz signal must
be fed in externally (ball F3).
This signal must be a
square wave
with following specifications:
Minimum
Maximum
Unit
L-input voltage
-0.25
+0.2
V
H-input voltage
1.8
2.2
V
Input impedence
> 10K
Ω
If ‘power saving’ and ‘Real Time Clock’ features are not required, the signal 32K_IN (ball F3) must be
connected to ground.
32K_IN
GE864
AUTO
ball
F3
SQUARE
WAVE
32.768KHz
