FEMTOCLOCK® LVCMOS/CRYSTAL-TO-3.3V, 2.5V LVPECL
FREQUENCY SYNTHESIZER
9 Rev B 12/9/14
843004I DATA SHEET
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 843004I provides separate
power supplies to isolate any high switching noise from the outputs
to the internal PLL. V
CC,
V
CCA
and V
CCO
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
CC
pin and also shows that V
CCA
requires that an
additional 10 resistor along with a 10F bypass capacitor be
connected to the V
CCA
pin.
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 1k resistor can be tied from
XTAL_IN to ground.
TEST_CLK Input
For applications not requiring the use of the clock, it can be left
floating. Though not required, but for additional protection, a 1k
resistor can be tied from the TEST_CLK to ground.
LVCMOS Control Pins
All control pins have internal pulldowns; additional resistance is not
required but can be added for additional protection. A 1k 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.
V
CC
V
CCA
3.3V or 2.5V
10Ω
10µF.01µF
.01µF
