SMSC FlexPWR LAN8720 - Manual (Page 33)

Small Footprint RMII 10/100 Ethernet Transceiver with HP Auto-MDIX Support
Datasheet
SMSC LAN8720/LAN8720i 33 Revision 1.0 (05-28-09)
DATASHEET
4.11 REGOFF and LED Polarity Selection
The REGOFF configuration pin 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 LED pin is pulled high to
VDD2A by an external pull-up resistor to select a logical high for REGOFF, then the LED output will
be active low. If the LED pin is pulled low by the internal pull-down resistor to select a logical low for
REGOFF, the LED output will then be an active high output.
To set REGOFF without LEDs, pull-up the pin with an external resistor to VDDIO to disable the
regulator. See
Figure 4.9 .
Figure 4.8 nINTSEL Strapping on LED2
Figure 4.9 REGOFF Configuration on LED1
~270 ohms
nINTSEL = 0
LED output = active high
10K
~270 ohms
VDD2A
nINTSEL = 1
LED output = active low
LED2/nINTSEL
LED2/nINTSEL
LED1/REGOFF
~270 ohms
REGOFF = 0
LED output = active high
~270 ohms
VDD2A
REGOFF = 1 (Regulator OFF)
LED output = active low
LED1/REGOFF
10K