Datasheet

 2009-2016 Microchip Technology Inc. DS00002306A-page 15
LAN9514/LAN9514I
enabled, creating an open drain output. If there is an over-current situation, the USB Power Switch will assert the open
drain OCS signal. The Schmitt trigger input will recognize this situation as a low. The open drain output does not inter-
fere. The overcurrent sense filter handles the transient conditions, such as low voltage, while the device is powering up.
2.2.2 PORT POWER CONTROL USING A POLY FUSE
When using the LAN9514/LAN9514i with a poly fuse, an external diode must be used (See Figure 2-4). When disabling
port power, the driver will drive a ‘0’. This procedure will have no effect since the external diode will isolate the pin from
the load. When port power is enabled, the output driver is disabled and the pull-up resistor is enabled, which creates an
open drain output. This means that the pull-up resistor is providing 3.3 volts to the anode of the diode. If there is an over-
FIGURE 2-3: PORT POWER CONTROL WITH USB POWER SWITCH
USB Power
Switch
EN
OCS
5V
USB
Device
LAN9514/
LAN9514i
PRTCTL3
USB Power
Switch
EN
OCS
5V
USB
Device
PRTCTL2
USB Power
Switch
EN
OCS
5V
USB
Device
PRTCTL4
USB Power
Switch
EN
OCS
5V
USB
Device
PRTCTL5