ICS84427 View Datasheet(PDF) - Integrated Circuit Systems
Part Name
Description
MFG CO.
'ICS84427' PDF : 13 Pages View PDF
Integrated
Circuit
Systems, Inc.
PRELIMINARY
ICS84427
CRYSTAL-TO-LVDS
INTEGRATED FREQUENCY SYNTHESIZER/FANOUT BUFFER
APPLICATION INFORMATION
POWER SUPPLY FILTERING TECHNIQUES
As in any high speed analog circuitry, the power supply pins
are vulnerable to random noise. The ICS84427 provides sepa-
rate power supplies to isolate any high switching
noise from the outputs to the internal PLL. VDD and VDDA should
be individually connected to the power supply plane through
vias, and bypass capacitors should be used for each pin. To
achieve optimum jitter performance, power supply isolation is
required. Figure 1 illustrates how a 24Ω resistor along with a
10μF and a .01μF bypass capacitor should be connected to
each VDDA pin.
VDD
VDDA
3.3V
.01μF 24Ω
.01μF
10 μF
FIGURE 1. POWER SUPPLY FILTERING
CRYSTAL INPUT INTERFACE
The ICS84427 has been characterized with 18pF parallel
resonant crystals. The capacitor values, C1 and C2, shown
in Figure 2 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.
X1
18pF Parallel Crystal
XTAL_IN
C1
18p
XTAL_OUT
C2
22p
Figure 2. CRYSTAL INPUt INTERFACE
84427CM
www.icst.com/products/hiperclocks.html
7
REV. D NOVEMBER 30, 2005
Share Link: 
