1893CKLFT IDT, 1893CKLFT Datasheet - Page 20

• Manufacturer Part Number: 1893CKLFT
• Description: Ethernet ICs 3.3V 10/100 BASE TX INTEGRATED PHYCEIVER
• Manufacturer: IDT

Specifications of 1893CKLFT

• Rohs: yes
• Part # Aliases: ICS1893CKLFT

5.4 Clock Reference Interface
ICS1893CK-40, Rev. C, 06/02/09
Oscillator
The REF_IN pin provides the ICS1893CK-40 Clock Reference Interface. The ICS1893CK-40 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 ICS1893CK-40 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
ICS1893CK-40 Data Sheet - Release
25.000
33 pF
CMOS
MHz
REF_OUT
REF_OUT
46
NC
46
ICS1893CK-4
ICS1893CK-4
25.000MHz
Copyright © 2009, Integrated Device Technology, Inc.
33 Ohm
REF_IN
REF_IN
All rights reserved.
47
47
20
33 pF
10 pF
Chapter 5 Interface Overviews
June 2009