元器件交易网
PRELIMINARY
IntegratedCircuit
Systems, Inc.
CRYSTAL-TO-LVCMOS / LVTTL
FREQUENCY SYNTHESIZER WITH FANOUT BUFFER
APPLICATION INFORMATION
ICS84025
POWER SUPPLY FILTERING TECHNIQUES
As in any high speed analog circuitry, the power supply pinsare vulnerable to random noise. The ICS84025 provides sepa-rate power supplies to isolate any high switchingnoise from the outputs to the internal PLL. VDD, VDDA, and VDDOshould be individually connected to the power supplyplane through vias, and bypass capacitors should beused for each pin. To achieve optimum jitter performance,power supply isolation is required. Figure 2 illustrates howa 24 resistor along with a 10µF and a .01µF bypasscapacitor should be connected to each VDDA pin.
IGUREOWERUPPLYILTERING
CRYSTAL INPUT INTERFACE
A crystal can be characterized for either series or parallelmode operation. The ICS84025 has a built-in crystal oscillatorcircuit. This interface can accept either a series or parallelcrystal without additional components and generate
frequencies with accuracy suitable for most applications.Additional accuracy can be achieved by adding two smallcapacitors C1 and C2 as shown in Figure 3.
84025EM
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REV. A APRIL 16, 2003