LAN9514_12 Datasheet, PDF (17/52 Pages) SMSC Corporation – USB 2.0 Hub and 10/100 Ethernet Controller

USB 2.0 Hub and 10/100 Ethernet Controller
Datasheet
2.2
2.2.1
Port Power Control
This section details the usage of the port power control pins PRTCTL[5:2].
Port Power Control Using a USB Power Switch
The LAN9514/LAN9514i 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.
5V
OCS
USB Power
Switch
EN
PRTCTL4
PRTCTL3
5V
OCS
USB Power
Switch
EN
USB
Device
LAN9514/
LAN9514i
USB
Device
5V
OCS
USB Power
Switch
EN
PRTCTL5
PRTCTL2
5V
OCS
USB Power
Switch
EN
USB
Device
USB
Device
Figure 2.3 Port Power Control with USB Power Switch
SMSC LAN9514/LAN9514i
17
DATASHEET
Revision 1.2 (02-29-12)