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6.0
Oscillator Support
The 82563EB/82564EB clock input circuit is optimized for use with an external crystal. However,
an oscillator can also be used in place of the crystal with the proper design considerations:
•
The clock oscillator has an internal voltage regulator of 1.2 V to isolate it from the external
noise of other circuits to minimize jitter. If an external clock is used, this imposes a maximum
input clock amplitude of 1.2 V.
•
The input capacitance introduced by the 82563EB/82564EB (approximately 20 pF) is greater
than the capacitance specified by a typical oscillator (approximately 15 pF).
•
The input clock jitter from the oscillator can impact the 82563EB/82564EB clock and its
performance.
Table 10. 82563EB/82564EB Clock Oscillator Specifications
Symbol
f0
df0
Dc
tr
tf
σi
C1
VDD
Operating
temperature
CMOS output
levels
Note: The power consumption of additional circuitry equals about 1.5 mW.
The following table lists oscillators which have been used successfully in past designs (however no
particular product is recommended):
Table 11. Oscillator Manufacturers and Part Numbers
Manufacturer
RALTRON
CITIZEN AMERICA CORP
82563EB/82564EB LAN on Motherboard Design Guide
Parameter
Frequency
Frequency Variation
Duty Cycle
Rise Time
Fall Time
Clock Jitter, rms (if specified)
Clock Capacitance (pushed by clock)
Supply Voltage
-
Voltage Output High (V
),
oh
Voltage Output Low (V
)
ol
Part No.
CO4305-25.000-TR
CSX750FBB25.000MTR
Specifications
Min
Typical
Max
-
25
-
-50
-
+50
40
-
60
-
-
5
-
-
5
-
-
50
-
15
50
-
3.3
-
-
-
70
80% VDD
-
20% VDD
Units
MHz
ppm
%
ns
ns
ps
pF
V
° C
V
V
23
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