SC2200 NSC [National Semiconductor], SC2200 Datasheet - Page 117

• Manufacturer Part Number: SC2200
• Description: Thin Client On a Chip
• Manufacturer: NSC [National Semiconductor]

Revision 3.0
SuperI/O Module
4.5.2.6
The device is supplied from two supply voltages, as shown
in Figure 4-8:
• System standby power supply voltage, V
• Backup voltage, from low capacity Lithium battery
A standby voltage, V
supply powers the RTC under normal conditions.
Figure 4-9 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
V
Note:
ACPI Controller
PP
Figure 4-9. Typical Battery Configuration
RTC
Figure 4-8. Power Supply Connections
Power Supply
Place a 0.1 F capacitor on each V
power supply pin as close as possible to the
pin, and also on V
V
V
PC0
V
DIGITAL
BAT
SB
RTC
Sense
V
SB
V
BAT
SB
V
, from the external AC/DC power
(Continued)
REF
BAT
.
V
ONCTL#
DIGITAL
V
V
V
BAT
R
V
V
SB
BAT
SBL
UL
SB
External AC Power
0.1 F
SB
ONCTL#
V
V
Supply
Backup
Power
Battery
DIGITAL
SB
C
C
C
UL
F
F
F
SB
.
, V
0.1 F
SBL
0.1 F
BT
V
V
SBL
SB
1
117
The RTC is supplied from one of two power supplies, V
or V
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
minimum, as detailed in Section 8.0 "Electrical Specifica-
tions" on page 357.
The actual voltage point where the module switches from
V
voltage, but high enough to guarantee the correct function-
ality of the oscillator and the CMOS RAM.
Figure 4-10 shows typical battery current consumption dur-
ing battery-backed operation, and Figure 4-11 during nor-
mal operation.
BAT
Figure 4-10. Typical Battery Current: Battery
Figure 4-11. Typical Battery Current: Normal
BAT
to V
0.75
0.50
0.25
BAT
, according to their levels. An internal voltage com-
I
Note: Battery voltage in this test is 3.0V.
BAT
Backed Power Mode @ T
, the V
SB
10.0
( A)
I
is lower than the minimum workable battery
BAT
7.5
5.0
2.5
3.0 3.3 3.6
SB
( A)
voltage should be maintained above its
Operation Mode
2.4 3.0 3.6
SB
BAT
main battery.
maintains the correct time and
V
SB
BAT
C
V
(V)
voltage is absent,
SB
= 25°C
(V)
www.national.com
SB
and not
SB