ICS83905I Datasheet, PDF (11/16 Pages) Integrated Circuit Systems – LOW SKEW, 1:6 CRYSTAL INTERFACE-TO LVCMOS/LVTTL FANOUT BUFFER

Integrated
Circuit
Systems, Inc.
ICS83905I
LOW SKEW, 1:6 CRYSTAL INTERFACE-TO-
LVCMOS / LVTTL FANOUT BUFFER
APPLICATION INFORMATION
CRYSTAL INPUT INTERFACE
Figure 1A shows an example of ICS83905I crystal interface with
a parallel resonant crystal. The frequency accuracy can be fine
tuned by adjusting the C1 and C2 values. For a parallel crystal
with loading capacitance CL = 18pF, we suggest C1 = 15pF and
C2 = 15pF to start with. These values may be slightly fine tuned
further to optimize the frequency accuracy for different board lay-
outs. Slightly increasing the C1 and C2 values will slightly reduce
the frequency. Slightly decreasing the C1 and C2 values will slightly
increase the frequency. For the oscillator circuit below, R1 can
be used, but is not required. For new designs, it is recommended
that R1 not be used.
C1
15p
X1
18pF Parallel Cry stal
0
C2
R1 (optional)
15p
XTAL_IN
XTAL_OUT
FIGURE 1. CRYSTAL OSCILLATOR INTERFACE
83905AGI
http://www.icst.com/products/hiperclocks.html
11
REV. B MAY 16, 2005