PI5L100 查看數據表（PDF） - Pericom Semiconductor Corporation
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PI5L100 Datasheet PDF : 13 Pages
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PI5L100
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APPLICATIONS SECTION
LAN Switch Applications
The PI5L100 was designed to switch between various
standards such as 10Base-T, 100Base-T, 100VG-
AnyLAN, and Token Ring. Also general purpose
applications such as loopback, line termination, and line
clamps that might normally use mechanical relays are
also ideal uses for this LAN Switch (see Figure 11
applications). Generally speaking, this LAN Switch can
be used for data rates to 200 Mbps and data signal levels
from 0V to 4.5V.
LAN Standards
10Base-T
100Base-T
100VG-AnyLAN
Data Rate per twisted pair (UTP)
10 Mbps
100 Mbps
25 Mbps
Differential Crosstalk ...XTALK (DIF)
Adjacent pins cause the most crosstalk because of the
interlead package capacitance which is generally in the
order of 0.5 pF (pin-to-pin). It can be seen in Figure 11
that this Evaluation (EV) Board schematic uses four
pairs of switches. The pair 1B/2B are RX1 that connect
to YA and YB. The second pair 3B/4B are TX1 and
connect to YC and YB. Pairs 3 and 4 are grounded for
this differential crosstalk test. The purpose of this EV
board is to determine the amont of crosstalk between the
transmit and receive pairs in a full duplex application.
Figure 15 shows the scope waveforms. Traces 1 and 2
are single ended inputs to the differential inputs of the
DUT. Trace 3 is the differential XTALK output which
equates to 20LOG VOUT/VIN = 20LOG 30 mV/5V = –
44dB. Since the edge rate is 2 ns, the effective input
frequency is equal to 0.3/tR which is ~150 MHz. So the
approximate Differential Crosstalk at 150 MHz is
–44dB.
Because pins measured are not adjacent, the differential
crosstalk is typically > 60 dB at 10 MHz. The load
resistor (RL) used was 100 ( to match the UTP imped-
ance). Increasing the data rate or RL will also increase
differential crosstalk.
VCC Bias Voltage vs RON
To keep RON to a minimum, it is recommended that the
VCC voltage be increased to a voltage between +6.0V
and +6.5V (see Figure 13). The RON vs VIN curve shows
the effect of on-resistance and input voltage which is
exponential. Ideally an input voltage between 0.2V and
3.6V will keep RON in the flat part of the curve (∆RON or
flatness is ~2Ω).
Signal Distortion
Distortion of the input signal is equated to 20LOG ∆RON/
RL. So keeping RON flat as the data signal level varies
is critical to low distortion. It should also be noted that
increasing the data rate increases harmonic distortion
which also effects the signal amplitude.
Evaluation Board
Figure 14 shows the layout for an EV board that can be
used for evaluation. This is a 2-layer board and is one-
inch square.
223
PS7031B 04/29/97
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