SMSC FlexPWR LAN8720 - Manual (Page 28)

Small Footprint RMII 10/100 Ethernet Transceiver with HP Auto-MDIX Support
Datasheet
Revision 1.0 (05-28-09) 28 SMSC LAN8720/LAN8720i
DATASHEET
In some system architectures, a 25MHz clock source is available. The LAN8720 can be used to
generate the REF_CLK to the MAC as shown in
Figure 4.6 . It is important to note that in this specific
Figure 4.5 LAN8720 sources REF_CLK from a 25MHz crystal
LAN8720
10/100 PHY
24-QFN
RMII
TXP
TXN
Mag RJ45
RXP
RXN
25MHz
XTAL1/CLKIN
XTAL2
LED[2:1]
2
Interface
nRST
TXD[1:0]
2
RXD[1:0]
CRS_DV
2
RMII
MDIO
MDC
TXEN
REFCLKO
MAC
Capable of
accepting 50MHz
clock
nINT not available in this
configuration
RXER
REF_CLK