7 / 12 page
FS781/82/84
Document #: 38-07029 Rev. *E
Page 7 of 12
**
** Occasionally, C8 is used to
create a second pole for this loop
filter. Refer to Loop Filter Selection
table.
Mount loop filter components as
close to LF pin as possible.
.
Crystal is 20 MHz is 1st Order
with 18 pF load capacitance.
If Crystal load capacitance is
different than 18 pF, C1 and C2
must be re-calculated.
For third overtone crystals, a
parallel or series resonant trap
is required.
R6
C1
0.1 uF
C2
27 pF
C3
27 pF
Y1
20 MHz
C8
C7
FS781
(SOIC)
Xin
1
Xout
2
S1
3
LF
4
VSS
5
FSOUT
6
S0
7
VDD
8
VDD
FSOUT
Figure 5. FS781 Schematic
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