843003AGLF Datasheet, PDF (12/21 Pages) Integrated Device Technology – FEMTOCLOCKS™ CRYSTAL-TO-3.3V LVPECL FREQUENCY SYNTHESIZER

ICS843003
FEMTOCLOCKS™ CRYSTAL-TO-3.3V LVPECL FREQUENCY SYNTHESIZER
Application Information
Power Supply Filtering Technique
As in any high speed analog circuitry, the power supply pins are
vulnerable to random noise. To achieve optimum jitter
performance, power supply isolation is required. The ICS843003
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 0.01µF bypass capacitors should be used for
each pin. Figure 2 illustrates this for a generic V_CC pin and also
shows that V_CCA requires that an additional 10Ω resistor along with
a 10µF bypass capacitor be connected to the V_CCA pin.
3.3V
V_CC
.01µF _10Ω
V_CCA
.01µF
10µF
Figure 2. 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.
TEST_CLK Input
For applications not requiring the use of the test clock, it can be left
floating. Though not required, but for additional protection, a 1kΩ
resistor can be tied from the TEST_CLK to ground.
LVCMOS Control Pins
All control pins have internal pull-ups or pull-downs; additional
resistance is not required but can be added for additional
protection. A 1kΩ resistor can be used.
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.
IDT™ / ICS™ LVPECL FREQUENCY SYNTHESIZER
12
ICS843003AG REV. A OCTOBER 23, 2008