Datasheet

USB 2.0 Hub and 10/100 Ethernet Controller
Datasheet
SMSC LAN9512/LAN9512i 17 Revision 1.2 (02-29-12)
DATASHEET
2.2 Port Power Control
This section details the usage of the port power control pins PRTCTL[3:2].
2.2.1 Port Power Control Using a USB Power Switch
The LAN9512/LAN9512i 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
overcurrent sense filter handles the transient conditions, such as low voltage, while the device is
powering up.
Figure 2.3 Port Power Control with USB Power Switch
USB Power
Switch
EN
OCS
5V
USB
Device
LAN9512/
LAN9512i
PRTCTL3
USB Power
Switch
EN
OCS
5V
USB
Device
PRTCTL2