PI5L100
Wide-Bandwidth, Low-Voltage
LanSwitch Quad 2:1 Mux/Demux
7
PS7031F 09/17/04
Figure 7. Crosstalk vs Frequency
DIV
10.00
24681246812
NETWORK
A: REF
0.000
[dB]
B: REF
180.0
[deg]
MKR 10 074 746.057 Hz
T/R 519.486m dB
θ –90.2501 deg
RBW: 10 kHz ST: 4.05 sec RANGE: R = 0, T = 0dBm
PI5L100 XTALK 10 MHz
RL = 50 Ohm
DIV
36.00
START
STOP
1 000 000 . 000 Hz
300 000 000 . 000 Hz
0dB
–10dB
–20dB
–30db
–40dB
–50dB
–60dB
–70dB
–80dB
–90dB
–100dB
+180˚
+144˚
+108˚
+72˚
+36˚
0¡
–36˚
–72˚
–108˚
–144˚
–180˚
MAGNITUDE
PHASE
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 termina-
tion, 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 Data Rate per twisted pair (UTP)
10Base-T 10 Mbps
100Base-T 100 Mbps
100VG-AnyLAN 25 Mbps
Differential Crosstalk . . . X
TALK
(DIF)
Adjacent pins cause the most crosstalk because of the interlead
package capacitance which is generally in the order of 0.5pF (pin-
to-pin). It can be seen in Figure 11 that this Evaluation (EV) Board
schematic uses four pairs of switches. 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
amount of crosstalk between the transmit and receive pairs in a full
duplex application. Figure 15 shows the scope waveforms. Traces
Applications
1 and 2 are single ended inputs to the differential inputs of the DUT.
Trace 3 is the differential X
TALK
output which equates to 20LOG
V
OUT
/V
IN
= 20LOG 30 mV/5V = –44dB. Since the edge rate is 2ns,
the effective input frequency is equal to 0.3/t
R
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 (R
L
) used was 100
( to match the UTP impedance). Increasing the data rate or R
L
will
also increase differential crosstalk.
V
CC
Bias Voltage vs R
ON
To keep R
ON
to a minimum, it is recommended that the V
CC
voltage
be increased to a voltage between +6.0V and +6.5V (see Figure 13).
The R
ON
vs. V
IN
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 R
ON
in the flat part of the curve (∆R
ON
or flatness
is ~2 ohms).
Signal Distortion
Distortion of the input signal is equated to 20LOG ∆R
ON
/ RL. So
keeping R
ON
flat as data signal level varies is critical to low
distortion. Also, increasing the data rate increases harmonic distor-
tion 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.
