Specifications

Product Technical Specification & Customer Design Guidelines
Interfaces
3.17 VRTC (Backup Battery)
The Q64 Wireless CPU
®
provides an input / output to connect a Real Time Clock
power supply.
3.17.1 Features
This pin is used as a back-up power supply for the internal Real Time Clock. The RTC
is supported by the Wireless CPU
®
when VCC is available, but a back-up power
supply is needed to save date and hour when the VCC is switched off.
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WA_DEV_Q64_PTS_001-003 January 9, 2009
2.5V
regulator
1.8V
regulator
from VCC
to RTC
Q64
VRTC
Figure 35 : Real Time Clock power supply
If the RTC is not used, the pin can be left open.
If the VCC is available, the back-up battery can be charged by the internal 2.5V power
supply regulator.
Electrical characteristics of the signal
Parameter Minimum Typ Maximum Unit
Input voltage 1.85 2.5 V
Input current
consumption*
3.3 μA
Output voltage 2.45 V
Output current 2 mA
*Provided by a RTC back-up battery when Q64 is off and VCC = 0V.