USB2640I Standard Microsystems Corp., USB2640I Datasheet - Page 24

• Manufacturer Part Number: USB2640I
• Description: Industrial Temperature Usb 2.0 Flash Media Controller And Usb Hub Combo
• Manufacturer: Standard Microsystems Corp.

Revision 2.0 (10-03-08)
6.3
Port Power Control Using USB Power Switch
The USB2640i/USB2641i has a single port power control and over-current sense signal for each
downstream port. When disabling port power, the driver will actively drive a '0'. To avoid unnecessary
power dissipation, the internal pull-up resistor will be disabled at that time. When port power is
enabled, the output driver is disabled, and the pull-up resistor is 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 interfere.
The over-current sense filter handles the transient conditions, such as low voltage, while the device is
powering up.
Port Power Control
Figure 6.1 Port Power Control with USB Power Switch
USB2640i/
USB2641i
Industrial Temperature USB 2.0 Flash Media Controller and USB Hub Combo
DATASHEET
24
PRTCTL3
PRTCTL2
EN
EN
OCS
OCS
USB Power
USB Power
Switch
Switch
Device
Device
USB
USB
5V
5V
SMSC USB2640i/USB2641i