W6100 datasheet(138/149 Pages) WIZNET

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W6100 – Hardwired Dual TCP/IP Stack Controller

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Clock & Transformer Requirements

7.1

Quartz Crystal Requirements.

Table 10 Quartz Crystal

Parameter

Condition / Description

Min

Typ

Max

Unit

Frequency(F)

MHz

Frequency Tolerance

At 25

C

-50

+50

ppm

Frequency Stability

1 Year aging.

-50

+50

ppm

Load Capacitance (CL)

ESR = 30 Ω

Feedback Resistor (RF)

External resistor

Ω

Startup time

W6100 Reset

Trans-conductance(gm)

16.7

mA/V

Gain Margin (gainmargin)

gainmargin = gm / gmcrit

6.99

C0(1) : The Packaging Parasitic Shunt Capacitance.

CL(1) : Load Capacitance. eq) CL = (CL1 X CL2) / (CL1 X CL2) + Cs

CL1 , CL2 : External Capacitances of the circuit connected to the crystal (Typically, CL1 = CL2)

Cs : Stray Capacitance of printed circuit board and connections.

gmcrit : Oscillator loop critical gain. eq) gmcrit = 4 × (ESR + RExt) × (2πF)2 × (C0 + CL)2

ESR(1) : Maximal equivalent series resistance. eq) ESR = Rm X ( 1 + C0/CL)2

RExt : Resistor for limiting the drive level(DL) of the crystal.

DL(1) : The power dissipated in the crystal. Excess power can destroy the crystal.

RF(2) : Feedback resistor.

⚫

C0, CL, ESR and DL are provided by the crystal manufacturer.

⚫

The W6100 has no feedback resistor. Therefore, it must be inserted outside.

* Figure 37 shows Crystal circuit modeling.

Figure 37 Quartz Crystal Model

Table 11 Crystal Recommendation Characteristics

Parameter

Range

Frequency

25 MHz

Frequency Tolerance (at 25℃)

±30 ppm

Shunt Capacitance

7pF Max

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