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WM_PRJ_Q2686_PTS_001-010
June 30, 2009
Q2686 Wireless CPU
®
3.19
BAT-RTC (Backup Battery)
The Q2686 Wireless CPU
®
provides an input/output to connect a Real Time
Clock (RTC) power supply.
3.19.1
Interface Description
This pin is used as a back-up power supply for the internal Real Time Clock.
The RTC is supported by the Wireless CPU
®
when VBATT is available, but a
back-up power supply is needed to save date and time when VBATT is
switched off (VBATT = 0V).
2.5V
regulator
1.8V
regulator
from VBATT
to RTC
Q2686
BAT-RTC (Pin 7)
Figure 12: Real Time Clock power supply
If the RTC is not used, this pin can be left open.
If VBATT is available, the back-up battery can be charged by the internal 2.5V
power supply regulator.
Pin description
Signal
Pin number
I/O
I/O type
Description
BAT-RTC
7
I/O
Supply
RTC Back-up supply
Electrical characteristics of the signals
Parameter
Minimum Typ Maximum Unit
Input voltage
1.85
3.0
V
Input current
consumption*
3.3
μ
A
Output voltage
2.45
V
Output current
2
mA
*Provided by an RTC back-up battery when Wireless CPU
®
power supply is off (VBATT = 0V).
