
IDT / ICS 3.3V, 2.5V LVPECL/ LVCMOS FANOUT BUFFER
10
ICS8536CGI-33 REV. B OCTOBER 27, 2008
ICS8536I-33
LOW SKEW, 1-TO-6, CRYSTAL OSCILLATOR/LVCMOS-TO-3.3V, 2.5V LVPECL/LVCMOS FANOUT BUFFER
APPLICATION INFORMATION
FIGURE 2. CRYSTAL INPUt INTERFACE
CRYSTAL INPUT INTERFACE
The ICS8536I-33 has been characterized with 18pF parallel
resonant crystals. The capacitor values, C1 and C2, shown in
Figure 2 below were determined using an 18pF parallel resonant
crystal and were chosen to minimize the ppm error. These
same capacitor values will tune any 18pF parallel resonant
crystal over the frequency range and other parameters speci-
fied in this data sheet. The optimum C1 and C2 values can be
slightly adjusted for different board layouts.
INPUTS:
CRYSTAL INPUTS
For applications not requiring the use of the crystal oscillator input,
both XTAL_IN and XTAL_OUT can be left floating. Though not
required, but for additional protection, a 1k
Ω resistor can be tied
from XTAL_IN to ground.
CLK INPUT
For applications not requiring the use of a clock input, it can be
left floating. Though not required, but for additional protection, a
1k
Ω resistor can be tied from the CLK input to ground.
LVCMOS CONTROL PINS
All control pins have internal pull-ups or pull-downs; additional
resistance is not required but can be added for additional
protection. A 1k
Ω resistor can be used.
RECOMMENDATIONS FOR UNUSED INPUT AND OUTPUT PINS
OUTPUTS:
LVCMOS OUTPUTS
All unused LVCMOS output can be left floating. There should be
no trace attached.
LVPECL OUTPUTS
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.
C1
27p
X1
18pF Parallel Crystal
C2
27p
XTAL_OUT
XTAL_IN