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Ultra Fast USB 2.0 Multi-Format Flash Media Controller/USB Hub Combo
Revision 2.0 (10-03-08) 58 SMSC USB2640/USB2641
DATASHEET
Chapter 10 AC Specifications
10.1 Oscillator/Clock
Crystal: Parallel Resonant, Fundamental Mode, 24 MHz ± 100 ppm.
External Clock: 50% Duty cycle ± 10%, 24 MHz ± 100 ppm, Jitter < 100 ps rms.
Figure 10.1 Typical Crystal Circuit
Note: C
B
equals total board/trace capacitance.
Figure 10.2 Formula to find value of C
1
and C
21
XTAL1
(C
S1 =
C
B
+ C
XTAL
)
XTAL2
(C
S2 =
C
B
+ C
XTAL
)
C
1
C
2
C
L
1Meg
Crystal
(C
1
+ C
S1
) x (C
2
+ C
S2
)
(C
1
+ C
S1
+
C
2
+ C
S2
)
C
L
=