ICS1893CK ICST [Integrated Circuit Systems], ICS1893CK Datasheet - Page 20

• Manufacturer Part Number: ICS1893CK
• Description: 3.3-V 10Base-T/100Base-TX Integrated PHYceive
• Manufacturer: ICST [Integrated Circuit Systems]

5.4 Clock Reference Interface
ICS1893CF, Rev. F, 03/01/07
Oscillator
The REF_IN pin provides the ICS1893CF Clock Reference Interface. The ICS1893CF requires a single
clock reference with a frequency of 25 MHz ±50 parts per million. This accuracy is necessary to meet the
interface requirements of the ISO/IEEE 8802-3 standard, specifically clauses 22.2.2.1 and 24.2.3.4. The
ICS1893CF supports two clock source configurations: a CMOS oscillator or a CMOS driver. The input to
REF_IN is CMOS (10% to 90% VDD), not TTL. Alternately, a 25MHz crystal may be used. The Oscillator
specifications are shown in Table 5.2.
Figure 5-2. Crystal or Oscillator Operation
Crystal
ICS1893CF Data Sheet - Release
33 pF
CMOS
25.000
MHz
REF_OUT
REF_OUT
46
NC
46
ICS1893CF
25.000MHz
Copyright © 2007, Integrated Device Technology, Inc.
ICS1893CF
33 Ohm
REF_IN
REF_IN
All rights reserved.
47
47
20
33 pF
10 pF
Chapter 5 Interface Overviews
Mar. 2007