7

PI6CFGL402B

Low Power PCIe 3.0 Clock Generator with 4 HCSL Outputs

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www.pericom.com

03/03/15

C1

27pF

Crystal�(C

C2

27pF

XTAL_IN

XTAL_OUT

SaRonix-eCera

FL2500047

Application Notes

Crystal circuit connection

The following diagram shows crystal circuit connection with a parallel crystal. For the CL=18pF crystal, it

is suggested to use C1= 27pF, C2= 27pF. C1 and C2 can be adjusted to fine tune to the target ppm of crystal

oscillator according to different board layouts.

Crystal Oscillator Circuit

Recommended Crystal Specification

Pericom recommends:

a)GC2500003XTAL49S/SMD(4.0mm),25M,CL=18pF,+/-30ppm,http://www.pericom.com/pdf/datasheets/se/GC_GF.pdf

b)FY2500081,SMD5x3.2(4P),25M,CL=18pF,+/-30ppm,http://www.pericom.com/pdf/datasheets/se/FY_F9.pdf

c)FL2500047,SMD3.2x2.5(4P),25M,CL=18pF,+/-20ppm,http://www.pericom.com/pdf/datasheets/se/FL.pdf

X1

X2

Cb

C1

C2

Cj

Rd

Rf

Cb

Pseudo

sine

Cj

CL= crystal spec. loading cap.

Cj = chip in/output cap. (3~5pF)

Cb = PCB trace/via cap. (2~4pF)

C1,2 = load cap. components

Rd = drive level res. (100Ω)

ASIC

Final choose/trim C1=C2=2 *CL - (Cb +Cj) for the target +/-ppm

Example: C1=C2=2*(18pF) – (4pF+5pF)=27pF

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