L80223 LSI, L80223 Datasheet - Page 136

• Manufacturer Part Number: L80223
• Manufacturer: LSI

Specifications of L80223

• Lead Free Status / RoHS Status: Not Compliant

A.9 Oscillator
A-14
25 MHz
25 MHz
The L80227 requires a 25 MHz reference frequency for internal signal
generation. This 25 MHz reference frequency can be generated from an
external 25 MHz crystal connected between OSCIN and GND or from
applying an external 25 MHz clock to OSCIN.
If a crystal oscillator is used, it must be a high-capacitance crystal, such
as the Abracon ABLS or ABLS2, and it can be added between the
OSCIN pin and GND, as shown in
Figure A.6
If a non high-capacitance crystal is used, a 47-pF capacitor must be
added between the crystal and GND, as shown in
Figure A.7
The reason for using a 47 pF capacitor is that the resonant frequency
depends on the load capacitance the crystal sees. Because the chip load
capacitance is fairly high (around 30 pF), a capacitor in series with the
crystal shifts the frequency back to the desired value, Adding a serial
capacitor is a robust and practical approach to solving any frequency
offset problem without degrading oscillator performance.
Application Information
47 pF
Connecting the L80227 to a High-Capacitance Crystal
Connecting the L80227 to a Non High-Capacitance
Crystal
OSCIN
OSCIN
Copyright © 2000, 2001, 2002 by LSI Logic Corporation. All rights reserved.
L80227
L80227
Figure
A.6.
Figure
A.7.