LAN9250 datasheet(413/421 Pages) MICROCHIP

413 / 421 page

 2015 Microchip Technology Inc.

DS00001913A-page 413

LAN9250

19.7

Clock Circuit

The device can accept either a 25 MHz crystal or a 25 MHz single-ended clock oscillator (±50 ppm) input. If the single-

ended clock oscillator method is implemented, OSCO should be left unconnected and OSCI should be driven with a

clock signal that adheres to the specifications outlined throughout Section 19.0, "Operational Characteristics". See

Table 19-13 for the recommended crystal specifications.

Note 28:

The maximum allowable values for frequency tolerance and frequency stability are application dependent.

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 29:

Frequency Deviation Over Time is also referred to as Aging.

Note 30:

The total deviation for 100BASE-TX is ±50 ppm.

Note 31:

The minimum drive level requirement PW is reduced to 100 uW with the addition of a 500 Ω series resistor,

if CO 5pF, CL 12 pF and R180 Ω

Note 32:

0 °C for commercial version, -40 °C for industrial and extended industrial versions

Note 33:

+70 °C for commercial version, +85 °C for industrial version, +105 °C for extended industrial version

Note 34:

This number includes the pad, the bond wire and the lead frame. PCB capacitance is not included in this

value. The OSCI pin, OSCO 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.

TABLE 19-13: 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

802.3 Frequency Tolerance at

25oC

Ftol

±40

ppm

Note 28

802.3 Frequency Stability Over

Temp

Ftemp

±40

ppm

Note 28

802.3 Frequency Deviation Over

Time

Fage

±3 to 5

ppm

Note 29

802.3 Total Allowable PPM Bud-

get

±50

ppm

Note 30

Shunt Capacitance

Load Capacitance

Drive Level

300

Note 31

µW

Equivalent Series Resistance

100

Ω

Operating Temperature Range

Note 32

Note 33

OSCI Pin Capacitance

3 typ

Note 34

OSCO Pin Capacitance

3 typ

Note 34

LAN9250 Datasheet(PDF) 413 Page - Microchip Technology

LAN9250 Datasheet(HTML) 413 Page - Microchip Technology

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 ...More

Datasheet Download

Link URL