ICS84025中文资料(7)

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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7

REV. A APRIL 16, 2003

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