USB 2.0 HSIC Hi-Speed 4-Port Hub Controller
Datasheet
latencies in the tens of microseconds versus the much longer latencies of the traditional USB
suspend/resume in the tens of milliseconds. The supported LPM states are detailed in Table 8.3. For
additional information, refer to the USB 2.0 Link Power Management Addendum.
Table 8.3 LPM State Definitions
STATE
L2
DESCRIPTION
ENTRY/EXIT TIME TO L0
Entry: ~3 ms
Suspend
Sleep
Exit: ~2 ms
L1
L0
Entry: ~65 us
Exit: ~100 us
Fully Enabled (On)
-
Note: State change timing is approximate and is measured by change in power consumption.
Note: System clocks are stopped only in suspend mode or when power is removed from the device.
8.6
Suspend (SUSPEND)
When enabled, the SUSPEND signal can be used to indicate that the entire hub has entered the USB
suspend state and that VBUS current consumption should be reduced in accordance with the USB
specification. Selective suspend set by the host on downstream hub ports have no effect on this signal
because there is no requirement to reduce current consumption from the upstream VBUS. Suspend
can be used by the system to monitor and dynamically adjust how much current the PMIC draws from
VBUS to charge the battery in the system during a USB session. Because it is a level indication, it will
assert or negate to reflect the current status of suspend without any interaction through the SMBus.
A negation of this signal indicates no level suspend interrupt and device has been configured by the
USB Host. The full configured current can be drawn from the USB VBUS pin on the USB connector
for charging - up to 500mA - depending on descriptor settings. When asserted, this signal indicates a
suspend interrupt or that the device has not yet been configured by USB Host. The current draw can
be limited by the system according to the USB specification. The USB specification limits current to
100mA before configuration, and up to 12.5mA in USB suspend mode.
SMSC USB4604
57
Revision 1.0 (06-17-13)
DATASHEET
SMSC [ SMSC CORPORATION ]
