7

All trademarks are property of their respective owners.

www.pericom.com

03/03/15

PI6CFGL202B

Low Power PCIe 3.0 Clock Generator with 2 HCSL Outputs

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

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

Recommended Crystal Specification

a) FL2500047, SMD 3.2X2.5(4P), 25MHz, CL=18pF, +/-20ppm, http://www.pericom.com/pdf/datasheets/se/FL.pdf

b) FY2500091, SMD 5x3.2(4P), 25MHz, CL=18pF, +/-30ppm, http://www.pericom.com/pdf/datasheets/se/FY_F9.pdf

15-0025