lan8720 Standard Microsystems Corp., lan8720 Datasheet - Page 65

• Manufacturer Part Number: lan8720
• Description: Small Footprint Rmii 10/100 Ethernet Transceiver With Hp Auto-mdix Support
• Manufacturer: Standard Microsystems Corp.

Small Footprint RMII 10/100 Ethernet Transceiver with HP Auto-MDIX Support
Datasheet
SMSC LAN8720/LAN8720i
6.6
Crystal Cut
Crystal Oscillation Mode
Crystal Calibration Mode
Frequency
Frequency Tolerance @ 25
Frequency Stability Over Temp
Frequency Deviation Over Time
Total Allowable PPM Budget
Shunt Capacitance
Load Capacitance
Drive Level
Equivalent Series Resistance
Operating Temperature Range
LAN8720/LAN8720i
XTAL1/CLKIN Pin Capacitance
LAN8720/LAN8720i XTAL2 Pin
Capacitance
PARAMETER
LAN8720/LAN8720i can accept either a 25MHz crystal or a 25MHz single-ended clock oscillator
(±50ppm) input. If the single-ended clock oscillator method is implemented, XTAL2 should be left
unconnected and XTAL1/CLKIN should be driven with a nominal 0-3.3V clock signal. See
for the recommended crystal specifications.
Note 6.1
Note 6.2
Note 6.3
Note 6.4
Note 6.5
Note 6.6
Clock Circuit
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).
Frequency Deviation Over Time is also referred to as Aging.
The total deviation for the Transmitter Clock Frequency is specified by IEEE 802.3u as
±100 PPM.
0
+85
This number includes the pad, the bond wire and the lead frame. PCB capacitance is not
included in this value. The XTAL1/CLKIN pin, XTAL2 pin and PCB capacitance values are
required to accurately calculate the value of the two external load capacitors. The total load
capacitance must be equivalent to what the crystal expects to see in the circuit so that the
crystal oscillator will operate at 25.000 MHz.
o
C for extended commercial version, -40
o
C
o
Table 6.12 LAN8720/LAN8720i Crystal Specifications
C for extended commercial version, +85
SYMBOL
F
F
F
F
P
C
temp
C
R
fund
age
tol
W
O
L
1
DATASHEET
Note 6.4
MIN
300
Parallel Resonant Mode
-
-
-
-
-
-
-
-
-
-
65
Fundamental Mode
AT, typ
+/-3 to 5
25.000
20 typ
NOM
7 typ
3 typ
3 typ
o
C for industrial version.
-
-
-
-
-
-
o
C for industrial version.
Note 6.5
MAX
±50
±50
±50
30
-
-
-
-
-
-
-
UNITS
PPM
PPM
PPM
PPM
Ohm
MHz
uW
Revision 1.0 (04-15-09)
pF
pF
o
pF
pF
C
Note 6.1
Note 6.1
Note 6.2
Note 6.3
Note 6.6
Note 6.6
NOTES
Table 6.12