ICS1893Y-10 Datasheet, PDF (35/150 Pages) –

ICS1893Y-10 - Release
Chapter 5 Interface Overviews
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 ICS1893Y-10. 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 bypass caps serve to
adjust the final frequency of the crystal oscillation. Typical applications would use 33pF bypass caps. The
exact value will be affected by the board routing capacitance on Ref_in and Ref_out pins. Smaller bypass
capacitors raise the frequency of oscillation. Once the exact value of bypass 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 43) using a frequency counter with a 10 second
sample. Using TXCLK prevents affecting the crystal frequency by the measurement. The crystal
specification is shown in Table 5.3.
Table 5-3. 25MHz Crystal Specification
Specifications
Fundamental Frequency
(tolerance is sum of freq.,
temp., stability and aging.)
Freq. Tolerance
Input Capacitance
Symbol Minimum Typical Maximum
F0
24.99875 25.00000 25.00125
Unit
MHz
∆F/f
± 50 ppm
Cin
3
pF
Table 5-4. 25MHz Oscillator Specification
Specifications
Symbol Minimum Typical Maximum
Output Frequency
F0
Freq. Stability (including aging) ∆F/f
24.99875 25.00000 25.00125
± 50
Duty cycle CMOS level
Tw/T
35
65
one-half VDD
VIH
2.79
VIL
0.33
Period Jitter
Tjitter
500
Input Capacitance
CIN
3
Unit
MHz
ppm
%
Volts
Volts
pS
pF
ICS1893Y-10 Rev F 1/20/04
Copyright © 2004, Integrated Circuit Systems, Inc.
All rights reserved.
35
January, 2004