USB2660 Standard Microsystems Corp., USB2660 Datasheet - Page 24

• Manufacturer Part Number: USB2660
• Description: Ultra Fast Usb 2.0 Hub And Multi-format Flash Media Controller With Dual Sd Interfaces
• Manufacturer: Standard Microsystems Corp.

Revision 1.0 (06-09-09)
Port Power control using a Poly Fuse
When using the USB2660/USB2660i with a poly fuse, an external diode must be used (See
Figure
have no effect since the external diode will isolate the pin from the load. When port power is enabled,
the USB2660/USB2660i output driver is disabled, and the pull-up resistor is enabled which creates an
open drain output. This open drain output condition 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 zero volts. The anode of the diode will be at 0.7 volts, and
the Schmitt trigger input will register this as a low resulting in an over-current detection. The open drain
output does not interfere.
When using a single poly fuse to power all devices, note that for the ganged situation, all power control
pins must be tied together.
Figure 6.2 Port Power Control with a Single Poly Fuse and Multiple Loads
6.2). When disabling port power, the USB2660/USB2660i will drive a '0'. This procedure will
Figure 6.3 Port Power with Ganged Control with Poly Fuse
USB2660/60i
Ultra Fast USB 2.0 Hub and Multi-Format Flash Media Controller with Dual SD Interfaces
USB2660/60i
DATASHEET
24
PRTCTL2
PRTCTL3
PRTCTL3
PRTCTL2
Device
Device
USB
USB
5 V
5V
Device
USB
5 V
SMSC USB2660/USB2660i
Poly Fuse
Device
USB
Datasheet