USB3813 datasheet(55/68 Pages) SMSC

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USB 2.0 Hi-Speed 3-Port Hub Controller Optimized for Portable Applications

Datasheet

SMSC USB3813

Revision 1.0 (06-17-13)

DATASHEET

8.5

Hub Connect (HUB_CONN)

HUB_CONN is the equivalent of VBUS. The device will connect to the upstream host when either of

the following conditions are met:



If there is no I2C master present, the device will attach when HUB_CONN is high.



If there is an I2C master present, the device will wait until the master has configured the device

and signalled completion by setting USB_ATTACH in the STCD register. Once the USB_ATTACH

bit it set, the device will connect once HUB_CONN is high.

Refer to Section 5.1.9, "Hub Connect Stage (Hub.Connect)," on page 22 for additional information.

8.6

Link Power Management (LPM)

The device supports the L0 (On), L1 (Sleep), and L2 (Suspend) link power management states per

the USB 2.0 Link Power Management Addendum. These supported LPM states offer low transitional

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 8.5. For

additional information, refer to the USB 2.0 Link Power Management Addendum.

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.

8.7

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.

Table 8.5 LPM State Definitions

STATE

DESCRIPTION

ENTRY/EXIT TIME TO L0

Suspend

Entry: ~3 ms

Exit: ~2 ms

Sleep

Entry: ~65 us

Exit: ~100 us

Fully Enabled (On)

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