Specifications

WM_PRJ_Q2400_PTS_001 - 003
6th November 2002
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2.18 VCC_RTC (Real Time Clock)
2.18.1 Interface description
This pin is used as a back-up power supply for the internal Real Time Clock.
The RTC is supported by the module when powered on but a back-up power
supply is needed to save date and hour when the module is switched off.
If the RTC is not used this pin can be left open.
Pin description
Signal Pin number I/O I/O type Description
VCC_RTC 56 I/O Supply RTC Back-up supply
Operating conditions
Parameter Condition Min Max Unit
Input voltage 2 2.75 V
Input Current VCC=0V; t° = 25°C
VCC_RTC=2.5V
3 µA
Input Current VCC=0V; t°:-20°C / 55°C
VCC_RTC=2.5V
10 µA
Output voltage 2.4 2.75 V
Output current 2 mA
2.18.2 Typical implementation
2.18.2.1 Capacitor
VCC-RTC
Regulator
2.5 V
±
10%
(With very Low Iq)
+VBATT
470
1K
Ex : 470uF
Shottky
Diode
En
Vout
Gn
d
Vin
Estimated range with 470 µF Capacitor: ~30 seconds.