DM9601
USB to Ethernet MAC Controller with Integrated 10/100 PHY
48
Final
Version: DM9601-DS-F01
June 22, 2002
14. Application Notes
14.1 Network Interface Signal Routing
Place the transformer as close as possible to the RJ-45
connector. Place all the 50Ω resistors as close as
possible to the DM9601 RX± and TX± pins. Traces routed
from RX± and TX± to the transformer should run in close
pairs directly to the transformer. The designer should be
careful not to place the transmit pair across the receive pair.
As always, vias should be avoided as much as possible.
The network interface should be void of any signal other
than the TX± and RX± pairs between the RJ-45 to the
transformer and the transformer to the DM9601. There
should be no power or ground planes in the area under the
network side of the transformer to include the area under the
RJ-45 connector. (Refer to Figure 4 and 5.) Keep chassis
ground away from all active signals. The RJ-45 connector
and any unused pin should be tied to chassis ground
through a resistor divider network and a 2KV bypass
capacitor.
The Band Gap resistor should be placed as physically close
to pins 25 and 26 as possible. (Refer to Figure 1 and 2.)
The designer should not run any high-speed signal near the
Band Gap resistor placement.
14.2 10Base-T/100Base-TX Application
DM9601
RX+
RX-
TX+
TX-
BGGND
BGRES
Transformer
RJ45
1
2
8
3
4
5
6
7
1:1
1:1
75Ω
1%
75Ω
1%
75Ω
1%
75Ω
1%
3.3V AVCC
0.1µF
0.1µF
0.1µF
0.1µF
0.1µF/2KV
Chasis GND
6.8KΩ, 1%
50Ω
1%
50Ω
1%
50Ω
1%
50Ω
1%
3.3V AVCC
AGND
AGND
AGND
AGND
29
30
33
34
26
25
Figure 14-1
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