1893CFLFT IDT, 1893CFLFT Datasheet - Page 21

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

Specifications of 1893CFLFT

• Rohs: yes
• Part # Aliases: ICS1893CFLFT

ICS1893CK-40, Rev. C, 06/02/09
If a crystal is used as the clocking source, connect it to both the Ref_in (pin 47) and Ref_out (pin 46) pins
of the ICS1893CK-40. A pair of bypass capacitors on either side of the crystal are connected to ground.
The crystal is used in the parallel resonance or anti-resonance mode. The value of the load caps serve to
adjust the final frequency of the crystal oscillation. Typical applications would use 33pF load caps. The
exact value will be affected by the board routing capacitance on Ref_in and Ref_out pins. Smaller load
capacitors raise the frequency of oscillation. Once the exact value of load capacitance is established it will
be the same for all boards using the same specification crystal. The best way to measure the crystal
frequency is to measure the frequency of TXCLK (pin 37) using a frequency counter with a 1 second gate
time. Using the buffered output TXCLK prevents the crystal frequency from being affected by the
measurement. The crystal specification is shown in Table 5.1.
Table 5-1. 25MHz Crystal Specification
Table 5-2. 25MHz Oscillator Specification
Specifications
Fundamental Frequency
(tolerance is sum of freq.,
temp., stability and aging.)
Freq. Tolerance
Input Capacitance
Specifications
Output Frequency
Freq. Stability (including aging)
Duty cycle CMOS level
one-half VDD
VIH
VIL
Period Jitter
Input Capacitance
ICS1893CK-40 Data Sheet Rev. C - Release
Copyright © 2009, Integrated Device Technology, Inc.
Symbol Minimum
F0
∆
Cin
Symbol Minimum
F0
∆
Tw/T
Tjitter
CIN
F/f
F/f
24.99875 25.00000
24.99875 25.00000
All rights reserved.
21
2.79
35
Typical Maximum
Typical Maximum
3
3
25.00125
25.00125
±
±
0.33
500
50
50
65
Chapter 5 Interface Overviews
Volts
Volts
MHz
MHz
ppm
ppm
Unit
Unit
pS
pF
pF
%
June 2009