LAN8720A-CP-TR Standard Microsystems (SMSC), LAN8720A-CP-TR Datasheet - Page 34

• Manufacturer Part Number: LAN8720A-CP-TR
• Description: SMALL FOOTPRINT RMII 10/100 ETHERNET TR
• Manufacturer: Standard Microsystems (SMSC)

Specifications of LAN8720A-CP-TR

• Number Of Receivers: 1
• Protocols Supported: IEEE 802.3
• Operating Supply Voltage (typ): 1.8/2.5/3.3V
• Package Type: QFN
• Operating Temperature Classification: Commercial
• Mounting: Surface Mount
• Operating Temperature (max): 85C
• Operating Temperature (min): 0C
• Lead Free Status / Rohs Status: Compliant

Revision 1.0 (12-09-09)
3.7.4.1
3.7.4.2
Reference
50MHz
Clock
Accepts external
REF_CLK
REF_CLK In Mode
In REF_CLK In Mode, the 50MHz REF_CLK is driven on the XTAL1/CLKIN pin. A 50MHz source for
REF_CLK must be available external to the device when using this mode. The clock is driven to both
the MAC and PHY as shown in
REF_CLK Out Mode
To reduce BOM cost, the device includes a feature to generate the RMII REF_CLK signal from a low-
cost, 25MHz fundamental crystal. This type of crystal is inexpensive in comparison to 3
crystals that would normally be required for 50MHz. The MAC must be capable of operating with an
external clock to take advantage of this feature as shown in
In order to optimize package size and cost, the REFCLKO pin is multiplexed with the nINT pin. In
REF_CLK Out mode, the nINT functionality is disabled to accommodate usage of REFCLKO as a
50MHz clock to the MAC.
50MHz clock
MAC
Interface
RMII
Figure 3.5 External 50MHz clock sources the REF_CLK
2
2
2
Figure
DATASHEET
nINT
MDIO
MDC
TXD[1:0]
TXEN
RXD[1:0]
CRS_DV
RXER
LED[2:1]
nRST
3.5.
34
10/100 PHY
LAN8720
24-QFN
RMII
Small Footprint RMII 10/100 Ethernet Transceiver with HP Auto-MDIX Support
XTAL1/CLKIN
XTAL2
RXP
RXN
Figure
TXN
TXP
3.6.
Mag
All RMII signals are
synchronous to the supplied
clock
SMSC LAN8720/LAN8720i
rd
Datasheet
RJ45
overtone