Figure 5-8. Power Supply Connections; Figure 5-9. Typical Battery Configuration; Figure 5-10. Typical Battery Current: Battery Backed Power Mode @ T C = 25°C; Figure 5-11. Typical Battery Current: Normal Operation Mode - AMD Geode SC1200 Data Book

32579B
5.5.2.6 Power Supply
The device is supplied from two supply voltages, as shown
in Figure 5-8:
• System standby power supply voltage, V
• Backup voltage, from low capacity Lithium battery
A standby voltage, V , from the external AC/DC power
SB
supply powers the RTC under normal conditions.
Figure 5-9 represents a typical battery configuration. No
external diode is required to meet the UL standard, due to
the internal switch and internal serial resistor R
ACPI Controller
V Sense
DIGITAL
PC0
V
SB
RTC
V
SB
V
BAT
V
BAT

Figure 5-8. Power Supply Connections

RTC
V
PP
V
REF
Note: Place a 0.1 μF capacitor on each V
power supply pin as close as possible to the
pin, and also on V

Figure 5-9. Typical Battery Configuration

108
SB
.
UL
External AC Power
Power
Supply
V
DIGITAL
V
DIGITAL
ONCTL#
ONCTL#
V
SB
V
SB
V
BAT Backup
Battery
V
SB
V
C
F
0.1
V V
SBL
C
F
0.1
V
BAT
BT
R
C
UL
F
μF
0.1
, V
SB SBL
.
BAT
The RTC is supplied from one of two power supplies, V
or V , according to their levels. An internal voltage com-
BAT
parator delivers the control signals to a pair of switches.
Battery backup voltage V
saves the CMOS memory when the V
due to power failure or disconnection of the external AC/DC
input power supply or V
To assure that the module uses power from V
from V , the V
BAT SB
minimum, as detailed in Section 9.0 "Electrical Specifica-
tions" on page 365.
The actual voltage point where the module switches from
V to V is lower than the minimum workable battery
BAT SB
voltage, but high enough to guarantee the correct function-
ality of the oscillator and the CMOS RAM.
Figure 5-10 shows typical battery current consumption dur-
ing battery-backed operation, and Figure 5-11 during nor-
mal operation.
I (μA)
BAT
10.0
7.5
5.0
2.5
Figure 5-10. Typical Battery Current: Battery
Backed Power Mode @ T
SB
μF
I (μA)
BAT
SBL
μF
1 0.75
0.50
0.25
3.0 3.3 3.6
Note: Battery voltage in this test is 3.0V.
Figure 5-11. Typical Battery Current: Normal
AMD Geode™ SC1200/SC1201 Processor Data Book
SuperI/O Module
maintains the correct time and
BAT
voltage is absent,
SB
main battery.
SB
voltage should be maintained above its
V (V)
BAT
2.4 3.0 3.6
= 25°C
C
V
SB
(V)
Operation Mode
SB
and not
SB