ICS843001-21 Datasheet, PDF (8/15 Pages) Integrated Circuit Systems – FEMTOCLOCKS™ CRYSTAL-TO-3.3V LVPECL FREQUENCY SYNTHESIZER

Integrated
Circuit
Systems, Inc.
ICS843001-21
FEMTOCLOCKS™ CRYSTAL-TO-3.3V LVPECL
FREQUENCY SYNTHESIZER
APPLICATION INFORMATION
POWER SUPPLY FILTERING TECHNIQUES
As in any high speed analog circuitry, the power supply pins
are vulnerable to random noise. The ICS843001-21 provides
separate power supplies to isolate any high switching
noise from the outputs to the internal PLL. V_CC, V_CCA, and V_{CCO_x}
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 10Ω resistor along with a 10µF and a .01μF bypass
capacitor should be connected to each V_CCA. The 10Ω resis-
tor can also be replaced by a ferrite bead.
3.3V
V
CC
.01μF 10Ω
V
CCA
.01μF
10μF
FIGURE 1. POWER SUPPLY FILTERING
CRYSTAL INPUT INTERFACE
The ICS843001-21 has been characterized with 18pF paral-
lel resonant crystals. The capacitor values shown in Figure 2
below were determined using a 19.44MHz, 18pF parallel reso-
nant crystal and were chosen to minimize the ppm error.
X1
18pF Parallel Cry stal
XTAL_IN
C1
22p
XTAL_OUT
C2
22p
I^IC^CS^S8⁸4⁴3³⁰3⁰2^1-21
Figure 2. CRYSTAL INPUt INTERFACE
843001AG-21
www.icst.com/products/hiperclocks.html
8
REV. A OCTOBER 26, 2005