Small Footprint RMII 10/100 Ethernet Transceiver with HP Auto-MDIX Support
Datasheet
Note: nINT not available in
this configuration
LAN8720A/LAN8720Ai
MAC
RMII
MDIO
MDC
10/100 PHY
24-QFN
RMII
Capable of
accepting 50MHz
clock
TXD[1:0]
2
2
TXEN
Mag
RJ45
RXD[1:0]
TXP
TXN
CRS_DV
RXER
RXP
RXN
REF_CLK
REFCLKO
XTAL1/CLKIN
XTAL2
LED[2:1]
nRST
25MHz
2
Interface
Figure 3.8 Sourcing REF_CLK from a 25MHz Crystal
In some system architectures, a 25MHz clock source is available. The device can be used to generate
the REF_CLK to the MAC as shown in Figure 3.9. It is important to note that in this specific example,
only a 25MHz clock can be used (clock cannot be 50MHz). Similar to the 25MHz crystal mode, the
nINT function is disabled.
SMSC LAN8720A/LAN8720Ai
35
Revision 1.4 (08-23-12)
DATASHEET