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Ultra Fast USB 2.0 SD/MMC Flash Media Controller
Datasheet
Revision 1.0 (05-27-08) 20 SMSC USB2244/USB2244i
DATASHEET
Chapter 8 AC Specifications
8.1 Oscillator/Clock
Crystal: Parallel Resonant, Fundamental Mode, 24 MHz ± 100ppm.
External Clock: 50% Duty cycle ± 10%, 24 MHz ± 100ppm, Jitter < 100ps rms.
Figure 8.1 Typical Crystal Circuit
Note: C
B
equals total board/trace capacitance.
Figure 8.2 Formula to Find Value of C
1
and C
2
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
=