LAN8720A-CP SMSC, LAN8720A-CP Datasheet - Page 37

• Manufacturer Part Number: LAN8720A-CP
• Description: TXRX ETHERNET 10/100 RMII
• Manufacturer: SMSC
• Type: Transceiverr

Specifications of LAN8720A-CP

• Number Of Drivers/receivers: 4/4
• Protocol: RMII
• Voltage - Supply: 1.6 V ~ 3.6 V
• Mounting Type: Surface Mount
• Package / Case: 24-QFN
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: 638-1080

Small Footprint RMII 10/100 Ethernet Transceiver with HP Auto-MDIX Support
Datasheet
SMSC LAN8720A/LAN8720Ai
3.8
3.8.1
3.8.1.1
3.8.1.2
LEDs
Two LED signals are provided as a convenient means to determine the transceiver's mode of
operation. All LED signals are either active high or active low as described in
"nINTSEL and LED2 Polarity Selection"
on page
The LED1 output is driven active whenever the device detects a valid link, and blinks when CRS is
active (high) indicating activity.
The LED2 output is driven active when the operating speed is 100Mbps. This LED will go inactive
when the operating speed is 10Mbps or during line isolation.
Note: When pulling the LED1 and LED2 pins high, they must be tied to VDD2A, NOT VDDIO.
REGOFF and LED1 Polarity Selection
The REGOFF configuration strap is shared with the LED1 pin. The LED1 output will automatically
change polarity based on the presence of an external pull-up resistor. If the LED1 pin is pulled high to
VDD2A by an external pull-up resistor to select a logical high for REGOFF, then the LED1 output will
be active low. If the LED1 pin is pulled low by the internal pull-down resistor to select a logical low for
REGOFF, the LED1 output will then be an active high output.
each REGOFF configuration.
Note: Refer to
nINTSEL and LED2 Polarity Selection
The nINTSEL configuration strap is shared with the LED2 pin. The LED2 output will automatically
change polarity based on the presence of an external pull-down resistor. If the LED2 pin is pulled high
to VDD2A to select a logical high for nINTSEL, then the LED2 output will be active low. If the LED2
Miscellaneous Functions
10K
REGOFF = 1 (Regulator OFF)
LED output = Active Low
additional information on the REGOFF configuration strap.
VDD2A
37.
~270 ohms
Section 3.7.3, "REGOFF: Internal +1.2V Regulator Configuration," on page 32
Figure 3.10 LED1/REGOFF Polarity Configuration
LED1/REGOFF
DATASHEET
and
37
Section 3.8.1.1, "REGOFF and LED1 Polarity Selection,"
REGOFF = 0 (Regulator ON)
LED output = Active High
Figure 3.10
~270 ohms
LED1/REGOFF
details the LED1 polarity for
Revision 1.2 (11-10-10)
Section 3.8.1.2,
for