Small Footprint RMII 10/100 Ethernet Transceiver with HP Auto-MDIX Support
Datasheet
Chapter 1 Introduction
1.1
General Terms and Conventions
The following is list of the general terms used throughout this document:
BYTE
FIFO
8-bits
First In First Out buffer; often used for elasticity buffer
Media Access Controller
MAC
RMIITM
N/A
Reduced Media Independent InterfaceTM
Not Applicable
X
Indicates that a logic state is “don’t care” or undefined.
RESERVED
Refers to a reserved bit field or address. Unless otherwise
noted, reserved bits must always be zero for write
operations. Unless otherwise noted, values are not
guaranteed when reading reserved bits. Unless otherwise
noted, do not read or write to reserved addresses.
SMI
Serial Management Interface
1.2
General Description
The LAN8720A/LAN8720Ai is a low-power 10BASE-T/100BASE-TX physical layer (PHY) transceiver
with variable I/O voltage that is compliant with the IEEE 802.3-2005 standards.
The LAN8720A/LAN8720Ai supports communication with an Ethernet MAC via a standard RMII
interface. It contains a full-duplex 10-BASE-T/100BASE-TX transceiver and supports 10Mbps
(10BASE-T) and 100Mbps (100BASE-TX) operation. The LAN8720A/LAN8720Ai implements auto-
negotiation to automatically determine the best possible speed and duplex mode of operation. HP
Auto-MDIX support allows the use of direct connect or cross-over LAN cables.
The LAN8720A/LAN8720Ai supports both IEEE 802.3-2005 compliant and vendor-specific register
functions. However, no register access is required for operation. The initial configuration may be
selected via the configuration pins as described in Section 3.7, "Configuration Straps," on page 31.
Register-selectable configuration options may be used to further define the functionality of the
transceiver.
Per IEEE 802.3-2005 standards, all digital interface pins are tolerant to 3.6V. The device can be
configured to operate on a single 3.3V supply utilizing an integrated 3.3V to 1.2V linear regulator. The
linear regulator may be optionally disabled, allowing usage of a high efficiency external regulator for
lower system power dissipation.
The LAN8720A/LAN8720Ai is available in both extended commercial and industrial temperature range
versions. A typical system application is shown in Figure 1.1.
SMSC LAN8720A/LAN8720Ai
7
Revision 1.4 (08-23-12)
DATASHEET
SMSC [ SMSC CORPORATION ]
