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5.3
Subclock Generator
Connecting a 32.768-kHz Crystal Oscillator: Clock pulses can be supplied to the subclock
divider by connecting a 32.768-kHz crystal oscillator, as shown in figure 5.7. Follow the same
precautions as noted under 5.2 Notes on Board Design.
Figure 5.7 Typical Connection to 32.768-kHz Crystal Oscillator
Figure 5.8 shows the equivalent circuit of the 32.768-kHz crystal oscillator.
X
1
C
= 1.5 pF (typ.)
O
R
= 14 kΩ (typ.)
S
f
= 32.768 kHz
W
Note: Constants are reference values.
Figure 5.8 Equivalent Circuit of 32.768-kHz Crystal Oscillator
78
OSC
1
OSC
Open
2
Figure 5.6 Example of External Clock Input
X
1
X
2
L
C
S
External clock input
C
1
C = C = 15 pF (typ.)
1
2
C
2
S
C
O
R
S
X
2
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