Chapter
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3-9
voltage. It is usually calculated as 10% to 90% of Vout. The rise and fall edges
meet the following requirements:
3.0 ns
≤
trise/tfall
≤
5.0 ns, and maximum value of difference between trise and
tfall < 0.5 ns.
z
Waveform
overshoot
Waveform overshoot reflects the relationship between the stable value Vout and
the signal overshoot peak Vover (that is, the maximum change at the time of
transient relative to the stable value). The ratio of Vover to Vout meets the
following technical requirements:
Vover is less than 5% of Vout, and is attenuated to less than 1% within 8 ns.
z
Duty ratio distortion
Duty ratio distortion refers to pulse width change due to deformity and delay
during the signal transmission. This change changes the ratio of the duration
with pulses to that without any pulse. The duty ratio distortion of 100M Ethernet
interface must be less than ±0.5 ns.
z
Jitter
The output jitter of the 100M Ethernet interface should be less than 0.5 ns.
2) Receiver
interface
parameters
z
Differential mode input characteristic of receiver
The differential mode input characteristic of a receiver meets the technical
requirements for a twisted pair model stipulated in ANSI X3.263. For UTP, 5
models are available, and their attenuation values are respectively 5%, 25%,
50%, 75%, and 100% of the worst attenuation; but STP has one attenuation ratio:
100%.
z
Differential mode input impedance
This index is represented by feedback impedance. The nominal impedance of
UTP is 100
Ω
and that of STP is 150
Ω
. Within 2.0 to 80MHz, the impedance
feedback loss must meet the following requirements:
2 to 30 MHz: > 16 dB
30 to 60 MHz: > 16 – 20 log(f/30)dB f: frequency (MHz)
