234
Intel
®
855GME Chipset and Intel
®
6300ESB ICH Embedded Platform Design Guide
Intel
®
6300ESB Design Guidelines
9.11.1 RTC Crystal
The 6300ESB RTC module requires an external oscillating source of 32.768 kHz connected on the
RTCX1 and RTCX2 balls. Figure 129 shows the external circuitry that comprises the oscillator of
the 6300ESB RTC.
Figure 128. External Circuitry in the 6300ESB Without Use of Internal RTC
B1181-01
No
Connection
5 MΩ
RTCX2
Internal
External
RTCX1
32 kHz
Figure 129. External Circuitry for the 6300ESB RTC
NOTES:
1. The exact capacitor values for C1 and C2 must be based on the crystal maker recommendations. Typical
values for C1 and C2 are 18 pF, based on crystal load of 12.5 pF.
2. Reference designators are arbitrarily assigned.
3. 3.3 V Sus is active whenever the system is plugged in.
4. Vbatt is voltage provided by the battery.
5. VccRTC, RTCX1, and RTCX2 are 6300ESB pins.
6. VccRTC powers the 6300ESB RTC well.
7. RTCX1 is the input to the internal oscillator.
8. RTCX2 is the feedback for the external crystal.
9. VBIAS is used to provide a reference voltage, and this DC voltage sets a current, which is mirrored
throughout the oscillator and buffer circuitry.
10.Diodes must be Schottky
B2846-01
C2
18pF
C1
18pF
Vbatt
R1
10 M
Ω
1 K
Ω
32.768 kHz
Xtal
1 F
VCCRTC
3.3V Sus
C3
0.047 F
+
RTCX2
RTCX1
R2
10 M
Ω
VBIAS
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