Intel 6300ESB ICH, Design Manual

Page: 237 / 320

January 2007 237
Intel
®
855GME Chipset and Intel
®
6300ESB ICH Embedded Platform Design Guide
Intel
®
6300ESB Design Guidelines
Note: Refer to the 6300ESB I/O Controller Hub Datasheet for actual DC Current Characteristics.
The voltage of the battery may affect the RTC accuracy. In general, when the battery voltage
decays, the RTC accuracy also decreases. High accuracy may be obtained when the RTC voltage is
in the range of 3.0 V to 3.3 V.
The battery must be connected to the 6300ESB through an isolation Schottky diode circuit. The
Schottky diode circuit allows the 6300ESB RTC-well to be powered by the battery when the
system power is not available, but by the system power when it is available. To do this, the diodes
are set to be reverse biased when the system power is not available.
Figure 130 is an example of a
diode circuit that is used.
A standby power supply should be used in a desktop system to provide continuous power to the
RTC when available, which increases the RTC battery life and thereby the RTC accuracy.
Figure 130. Diode Circuit to Connect RTC External Battery
B1183-01
1 K
Ω
V
CC
RTC
V
CCSUS
3_3
1.0 µF
+
–