ICS843204I Datasheet, PDF (7/16 Pages) Integrated Circuit Systems – FEMTOCLOCKS™ CRYSTAL-TO-3.3V LVPECL FREQUENCY SYNTHESIZER

ICS843204I
FEMTOCLOCK™ 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. To achieve optimum jitter perfor-
mance, power supply isolation is required. The ICS843204I pro-
vides separate power supplies to isolate any high switching noise
from the outputs to the internal PLL. V_CC, V_{CCA_A}, V_{CCA_B}, V_{CCO_A}
and V should be individually connected to the power supply
CCO_B
plane through vias, and 0.01µF bypass capacitors should be used
for each pin. Figure 1 illustrates this for a generic V_CC pin and
also shows that V_CCA requires that an additional10Ω resistor
along with a 10µF bypass capacitor be connected to the V_CCA
pin.
VCC
VCCA_A
3.3V
.01µF
10Ω
10Ω
.01µF 10µF
VCCA_B
.01µF 10µF
FIGURE 1. POWER SUPPLY FILTERING
RECOMMENDATIONS FOR UNUSED INPUT AND OUTPUT PINS
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 1kΩ resistor can be tied
from XTAL_IN to ground.
OUTPUTS:
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.
CLK INPUTS
For applications not requiring the use of a clock input, it can be
left floating. Though not required, but for additional protection, a
1kΩ resistor can be tied from the CLK input to ground.
LVCMOS CONTROL PINS
All control pins have internal pullups or pulldowns; additional
resistance is not required but can be added for additional
protection. A 1kΩ resistor can be used.
IDT^™ / ICS^™ 3.3V LVPECL FREQUENCY SYNTHESIZER
7
ICS843204AGI REV. A MARCH 18, 2009