LAN9512I-JZX SMSC, LAN9512I-JZX Datasheet - Page 17

• Manufacturer Part Number: LAN9512I-JZX
• Description: Ethernet ICs Hi-Speed USB 2.0 Hub High 10/100 Ethernet
• Manufacturer: SMSC

Specifications of LAN9512I-JZX

• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

USB 2.0 Hub and 10/100 Ethernet Controller
Datasheet
SMSC LAN9512/LAN9512i
2.1.2
Port Power Control Using a Poly Fuse
When using the LAN9512/LAN9512i with a poly fuse, an external diode must be used (See
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-current situation, the
poly fuse will open. This will cause the cathode of the diode to go to 0 volts. The anode of the diode
will be at 0.7 volts, and the Schmidt trigger input will register this as a low, resulting in an overcurrent
detection. The open drain output does not interfere.
LAN9512/
LAN9512i
Figure 2.3 Port Power Control with Poly Fuse
DATASHEET
PRTCTL3
PRTCTL2
17
Device
Device
USB
USB
5V
5V
Poly Fuse
Poly Fuse
Revision 1.0 (11-24-09)
Figure
2.3).