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IDT / ICS LVCMOS/LVTTL FREQUENCY SYNTHESIZER
8
ICS840245AGI REV. B NOVEMBER 16, 2006
ICS840245I
FEMTOCLOCKS 1:5, CRYSTAL-TO-LVCMOS/LVTTL FREQUENCY SYNTHESIZER
APPLICATION INFORMATION
As in any high speed analog circuitry, the power supply pins
are vulnerable to random noise. The ICS840245I provides sepa-
rate power supplies to isolate any high switching
noise from the outputs to the internal PLL. V
DD, VDDA, and VDDO
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 10
resistor along with a 10F and a .01F bypass
capacitor should be connected to each V
DDA.
POWER SUPPLY FILTERING TECHNIQUES
FIGURE 1. POWER SUPPLY FILTERING
10
V
DDA
10
F
.01
F
3.3V or 2.5V
.01
F
V
DD
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 1k
resistor can be used.
RECOMMENDATIONS FOR UNUSED INPUT AND OUTPUT PINS
OUTPUTS:
LVCMOS OUTPUT:
All unused LVCMOS output can be left floating. There should be
no trace attached.