SMSC LAN8720 User Manual
Small Footprint RMII 10/100 Ethernet Transceiver with HP Auto-MDIX Support
Datasheet
SMSC LAN8720/LAN8720i
63
Revision 1.0 (05-28-09)
DATASHEET
6.3.2.2
10M RMII Transmit Timing (50MHz REF_CLK OUT)
6.4
RMII CLKIN Requirements
Figure 6.9 10M RMII Transmit Timing Diagram (50MHz REF_CLK OUT)
Table 6.9 10M RMII Transmit Timing Values (50MHz REF_CLK OUT)
PARAMETER
DESCRIPTION
MIN
TYP
MAX
UNITS
NOTES
T14.1
Transmit signals required setup to
rising edge of REFCLKO
rising edge of REFCLKO
7
ns
T14.2
Transmit signals required hold
after rising edge of REFCLKO
after rising edge of REFCLKO
2.5
ns
CLKIN frequency
50
MHz
Table 6.10 RMII CLKIN (REF_CLK) Timing Values
PARAMETER
DESCRIPTION
MIN
TYP
MAX
UNITS
NOTES
CLKIN frequency
50
MHz
CLKIN Frequency Drift
± 50
ppm
CLKIN Duty Cycle
40
60
%
CLKIN Jitter
150
psec
p-p – not RMS
REFCLKO
Data In -
TXD[1:0]
T
14.1
TX_EN
T
14.2
Valid Data