ICS1893BF Data Sheet Rev. E - Release
Chapter 9 DC and AC Operating Conditions
9.3 Recommended Component Values
Table 9-3. Recommended Component Values for ICS1893BF
Parameter
Minimum
Typical
Maximum
Tolerance
Units
MHz
Ω
Oscillator Frequency
10TCSR Resistor Value
100TCSR Resistor Value
LED Resistor Value
–
–
25
2.00k
–
–
± 50 ppm †
1%
1%
–
–
See Figure 9-1
1k
–
Ω
510
10k
Ω
† There are two IEEE Std. 802.3 requirements that drive 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. ICS1893BF 10TCSR and 100TCSR
Typical Board Layouts
10TCSR and 100TCSR Bias Resistors
ICS1893BF
VDD
18
10TCSR
19
100TCSR
20
12.1 KΩ 1%
VDD
10TCSR
100TCSR
1.54KΩ 1%
2.0KΩ 1%
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.
4. The VDD connection to the 12.1K resistor can connect to any VDD. The 12.1K resistor provides
negative feedback to compensate for VDD changes. Lowering the 12.1K value will lower the
100baseT amplitude.
5. The ICS1893BF 10baseT amplitude is below the IEEE spec but is adequate for 200m operation. This
is the effect of additional MUXes added for the Auto-MDIX function.
ICS1893BF, Rev. E, 8/11/09
August, 2009
Copyright © 2009, IDT, Inc.
All rights reserved.
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