ICS844008I Datasheet, PDF (7/18 Pages) Integrated Device Technology – FEMTOCLOCKS™ CRYSTAL-TO-LVDS FREQUENCY SYNTHESIZER

ICS844008I-01
FEMTOCLOCKS™ CRYSTAL-TO-LVDS 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 ICS844008I-01
provides separate power supplies to isolate any high switching
noise from the outputs to the internal PLL. V and V should
DD
DDA
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 pin and also shows
DD
that V_DDA requires that an additional10Ω 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.
OUTPUTS:
LVDS OUTPUTS
All unused LVDS outputs should be terminated with 100Ω resistor
between the differential pair.
IDT^™ / ICS^™ LVDS FREQUENCY SYNTHESIZER
7
ICS844008AYI-01 REV. B NOVEMBER 21, 2008