LAN9514 datasheet(15/54 Pages) MICROCHIP

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 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

OCS

USB

Device

LAN9514/

LAN9514i

PRTCTL3

USB Power

Switch

OCS

USB

Device

PRTCTL2

USB Power

Switch

OCS

USB

Device

PRTCTL4

USB Power

Switch

OCS

USB

Device

PRTCTL5

LAN9514 Datasheet(PDF) 15 Page - Microchip Technology