Integrated
Circuit
Systems, Inc.
ICS843-75
75MH
Z
, LVCMOS, LVPECL
D
UAL
O
UTPUT
O
SCILLATOR
A
PPLICATION
I
NFORMATION
R
ECOMMENDATIONS FOR
U
NUSED
O
UTPUT
P
INS
LVCMOS O
UTPUT
:
An unused LVCMOS output should be terminated with 100Ω
to ground as close as possible to the device.
LVPECL O
UTPUT
All unused LVPECL outputs can be left floating. We recommend
that there is no trace attached. Both sides of the differential
output pair should either be left floating or terminated.
C
RYSTAL
I
NPUT
I
NTERFACE
The ICS843-75 has been characterized with 18pF parallel
resonant crystals. The capacitor values, C1 and C2, shown in
Figure 1
below were determined using a 25MHz, 18pF parallel
resonant crystal and were chosen to minimize the ppm error.
The optimum C1 and C2 values can be slightly adjusted for
different board layouts.
XTAL_OUT
C1
12p
X1
18pF Parallel Cry stal
XTAL_IN
C2
12p
Figure 1. C
RYSTAL
I
NPU
t I
NTERFACE
843AG-75
www.icst.com/products/hiperclocks.html
6
REV. A JANUARY 9, 2006
ICS [ INTEGRATED CIRCUIT SYSTEMS ]
