ICS84329-01 Datasheet, PDF (10/20 Pages) Integrated Device Technology – 700MHZ, LOW JITTER, CRYSTAL-TO-3.3V DIFFERENTIAL LVPECL FREQUENCY SYNTHESIZER

ICS84329-01
700MHZ, LOW JITTER, CRYSTAL-TO-3.3V
DIFFERENTIAL LVPECL FREQUENCY SYNTHESIZER
CRYSTAL INPUT AND OSCILLATOR INTERFACE
The ICS84329-01 features an internal oscillator that uses an
external quartz crystal as the source of its reference frequency.
The oscillator is a series resonant, multi-vibrator type design. This
design provides better stability and eliminates the need for large
on chip capacitors. Though a series resonant crystal is preferred,
a parallel resonant crystal can be used. A parallel resonant mode
crystal used in a series resonant circuit will exhibit a frequency
of oscillation a few hundred ppm lower than specified. A few
hundred ppm translates to KHz inaccuracy. In general computing
applications, this level of inaccuracy is irrelevant. If better ppm
accuracy is required, an external capacitor can be added to a
quartz crystal in series to XTAL1. Figure 5A shows how to
interface with a crystal.
ICS84329-01
XTAL2
XTAL1
Figures 5A and 5B show various crystal parameters which are
recommended only as guidelines. Figure 5A shows how to inter-
face a capacitor with a parallel resonant crystal. Figure 5B shows
the capacitor value needed for the optimum ppm performance
over various series resonant crystal frequencies. For IA64/32
platforms which required a Raltron Parallel Resonant Quartz
crystal part #AS-16.66-18-SMD-T-M1, a 7pF series capacitor can
be used to better the ppm accuracy.
FIGURE 5A. CRYSTAL INTERFACE
NOTE: For crystal frequencies higher than 17MHz,
a series tuning capacitor is required for proper operation.
FIGURE 5B. Recommended tuning capacitance for various series
resonant crystals.
30 _10.000
25
20
15
10
5
12.000
14.318
16.000
20.000
24.000
0
10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25
Series Resonant Crystal Frequency (MHz)
84329AM-01
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REV. D AUGUST 7, 2010