ICS8422002I-01 Datasheet, PDF (8/15 Pages) Integrated Circuit Systems – FEMTOCLOCKS™ CRYSTAL-TO-LVHSTL FREQUENCY SYNTHESIZER

ICS8422002I-01
FEMTOCLOCKS™ CRYSTAL-TO-LVHSTL FREQUENCY SYNTHESIZER
Application Information
PRELIMINARY
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
ICS8422002I-01 provides separate power supplies to isolate any
high switching noise from the outputs to the internal PLL. V_DD,
V_DDA and V_DDO should be individually connected to the power
supply plane through vias, and 0.01µF bypass capacitors should
be used for each pin. Figure 1 illustrates this for a generic V_DD pin
and also shows that V_DDA requires that an additional 10Ω resistor
along with a 10µF bypass capacitor be connected to the V_DDA pin.
3.3V
V_DD
.01µF _10Ω
V_DDA
.01µF
10µF
Figure 1. Power Supply Filtering
Recommendations for Unused Input and Output Pins
Inputs:
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.
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.
REF_CLK INPUT
For applications not requiring the use of the reference clock, it can
be left floating. Though not required, but for additional protection,
a 1kΩ resistor can be tied from the REF_CLK to ground.
Outputs:
LVHSTL Outputs
All unused LVHSTL 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™ LVHSTL FREQUENCY SYNTHESIZER
8
ICS8422002AGI-01 REV. C NOVEMBER 1, 2007