ICS1893CF datasheet(100/126 Pages) ICST

100 / 126 page

ICS1893CF, Rev. F, 03/01/07

Mar. 2007

100

Chapter 9 DC and AC Operating Conditions

ICS1893CF Data Sheet - Release

9.3 Recommended Component Values *

† There are two IEEE Std. 802.3 requirements that define the tolerance for the frequency of the oscillator.

• Clause 22.2.2.1 requires the MII TX_CLK to have an accuracy of ± 100 ppm.

• Clause 24.2.3.4 is more stringent. It requires the code-bit timer to have an accuracy of 0.005% (that is, ±50 ppm).

Figure 9-1. ICS1893CF 10TCSR and 100TCSR

* For backward compatibillity, refer to the “1893C Alternate Schematic” application note.

Table 9-3. Recommended Component Values for ICS1893CF

Parameter

Minimum

Typical

Maximum

Tolerance

Units

Oscillator Frequency

–

± 50 ppm †

MHz

10TCSR Resistor Value

–

2.43k

–

Ω

100TCSR Resistor Value

–

See Figure 9-1

–1%

Ω

LED Resistor Value

510

10k

–

Ω

Note:

1. The bias resistor networks set the 10baseT and 100baseTX output amplitude levels.

2. Amplitude is directly related to current sourced out of the 10TCSR and 100TCSR pins.

3. Resistor values shown above are typical. User should check amplitudes and adjust for transformer effects

4. The VDD connection to the 18.2K resistor can connect to any VDD. The 18.2K resistor provides negative

feedback to compensate for VDD changes. Lowering the 18.2K value will lower the 100baseT amplitude.

Typical Board Layouts

10TCSR and 100TCSR Bias Resistors

ICS1893CF

VDD

10TCSR

100TCSR

2.43K

Ω 1%

VDD

18.2K

Ω 1%

10TCSR

1.82K

Ω 1%

100TCSR

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