12

www.pericom.com

P-0.1

02/27/13

PI6C49021

Low Power High Integration Clock Generator

All trademarks are property of their respective owners.

C1

27pF

Crystal�(C

C2

27pF

XTAL_IN

XTAL_OUT

SaRonix-eCera

CG2500003

Application Notes

Crystal circuit connection

The following diagram shows PI6C49021 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) GC2500003 XTAL 49S/SMD(4.0 mm), 25M, CL=18pF, +/-30ppm, http://www.pericom.com/pdf/datasheets/se/GC_GF.pdf

b) FY2500081, SMD 5x3.2(4P), 25M, CL=18pF, +/-30ppm, http://www.pericom.com/pdf/datasheets/se/FY_F9.pdf

c) FL2500047, SMD 3.2x2.5(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. (100ohm)

ASIC

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

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

13-0015