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Small Footprint RMII 10/100 Ethernet Transceiver with HP Auto-MDIX Support
Datasheet
Revision 1.0 (05-28-09) 10 SMSC LAN8720/LAN8720i
DATASHEET
1.3 Architectural Overview
The LAN8720/LAN8720i is compliant with IEEE 802.3-2005 standards (RMII Pins tolerant to 3.6V) and
supports both IEEE 802.3-2005 compliant and vendor-specific register functions. It contains a full-
duplex 10-BASE-T/100BASE-TX transceiver and supports 10-Mbps (10BASE-T) operation, and 100-
Mbps (100BASE-TX) operation. The LAN8720/LAN8720i can be configured to operate on a single 3.3V
supply utilizing an integrated 3.3V to 1.2V linear regulator. An option is available to disable the linear
regulator to optimize system designs that have a 1.2V power supply available. This allows for the use
of a high efficiency external regulator for lower system power dissipation.
1.3.1 Configuration
The LAN8720 will begin normal operation following reset, and no register access is required. The initial
configuration may be selected with configuration pins as described in Section 5.3.9. In addition,
register-selectable configuration options may be used to further define the functionality of the
transceiver. For example, the device can be set to 10BASE-T only. The LAN8720 supports both IEEE
802.3-2005 compliant and vendor-specific register functions.
Figure 1.1 LAN8720/LAN8720i System Block Diagram
LAN8720
Ethernet
Transceiver
MODE
RMII
LED Status
10/100
Ethernet
MAC
Crystal or
Clock Osc
MDI
Transformer RJ45