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LAN9311 Datasheet, PDF (455/461 Pages) SMSC Corporation – Two Port 10/100 Managed Ethernet Switch with 16-Bit Non-PCI CPU Interface
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15.6
Two Port 10/100 Managed Ethernet Switch with 16-Bit Non-PCI CPU Interface
Datasheet
Clock Circuit
The LAN9311/LAN9311i can accept either a 25MHz crystal (preferred) or a 25MHz single-ended clock
oscillator (+/- 50ppm) input. If the single-ended clock oscillator method is implemented, XO should be
left unconnected and XI should be driven with a nominal 0-3.3V clock signal. The input clock duty cycle
is 40% minimum, 50% typical and 60% maximum.
It is recommended that a crystal utilizing matching parallel load capacitors be used for the crystal
input/output signals (XI/XO). See Table 15.15 for crystal specifications.
Table 15.15 LAN9311/LAN9311iCrystal Specifications
PARAMETER
Crystal Cut
Crystal Oscillation Mode
Crystal Calibration Mode
Frequency
Frequency Tolerance @ 25oC
Frequency Stability Over Temp
Frequency Deviation Over Time
Total Allowable PPM Budget
Shunt Capacitance
Load Capacitance
Drive Level
Equivalent Series Resistance
Operating Temperature Range
n/a XI Pin Capacitance
n/a XO Pin Capacitance
SYMBOL
Ffund
Ftol
Ftemp
Fage
CO
CL
PW
R1
MIN
NOM
MAX
AT, typ
Fundamental Mode
Parallel Resonant Mode
-
25.000
-
-
-
+/-50
-
-
+/-50
-
+/-3 to 5
-
-
-
+/-50
-
-
300
-
Note 15.16
7 typ
20 typ
-
-
-
-
-
-
50
Note 15.17
-
3 typ
-
-
3 typ
-
UNITS
MHz
PPM
PPM
PPM
PPM
pF
pF
uW
Ohm
oC
pF
pF
NOTES
Note 15.12
Note 15.12
Note 15.13
Note 15.14
Note 15.15
Note 15.15
Note 15.12 The maximum allowable values for Frequency Tolerance and Frequency Stability are
application dependant. Since any particular application must meet the IEEE +/-50 PPM
Total PPM Budget, the combination of these two values must be approximately +/-45 PPM
(allowing for aging).
Note 15.13 Frequency Deviation Over Time is also referred to as Aging.
Note 15.14 The total deviation for the Transmitter Clock Frequency is specified by IEEE 802.3 as
+/- 50 PPM.
Note 15.15 This number includes the pad, the bond wire and the lead frame. PCB capacitance is not
included in this value. The XO/XI pin and PCB capacitance values are required to
accurately calculate the value of the two external load capacitors. These two external load
capacitors determine the accuracy of the 25.000 MHz frequency.
Note 15.16 0oC for commercial version (LAN9311), -40oC for industrial version (LAN9311I)
Note 15.17 +70oC for commercial version (LAN9311), +85oC for industrial version (LAN9311I)
SMSC LAN9311/LAN9311i
455
DATASHEET
Revision 2.0 (02-14-13)
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