LAN9313 datasheet(394/398 Pages) SMSC

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Three Port 10/100 Managed Ethernet Switch with MII

Datasheet

Revision 1.2 (04-08-08)

394

SMSC LAN9313/LAN9313i

DATASHEET

14.6

Clock Circuit

The LAN9313/LAN9313i 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 14.10 for crystal specifications.

Note 14.12

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 14.13

Frequency Deviation Over Time is also referred to as Aging.

Note 14.14

The total deviation for the Transmitter Clock Frequency is specified by IEEE 802.3 as

+/- 50 PPM.

Note 14.15

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 14.16

+70oC for commercial version (LAN9313), +85oC for industrial version (LAN9313I)

Table 14.10 LAN9313/LAN9313i Crystal Specifications

PARAMETER

SYMBOL

MIN

NOM

MAX

UNITS

NOTES

Crystal Cut

AT, typ

Crystal Oscillation Mode

Fundamental Mode

Crystal Calibration Mode

Parallel Resonant Mode

Frequency

Ffund

25.000

MHz

Frequency Tolerance @ 25oCFtol

+/-50

PPM

Note 14.12

Frequency Stability Over Temp

Ftemp

+/-50

PPM

Note 14.12

Frequency Deviation Over Time

Fage

+/-3 to 5

PPM

Note 14.13

Total Allowable PPM Budget

+/-50

PPM

Note 14.14

Shunt Capacitance

-7 typ-

Load Capacitance

20 typ

Drive Level

0.5

Equivalent Series Resistance

Ohm

Operating Temperature Range

+70Note 1

4.16

n/a XI Pin Capacitance

3 typ

Note 14.15

n/a XO Pin Capacitance

3 typ

Note 14.15

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