USB5734 datasheet(38/61 Pages) MICROCHIP

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USB5734

DS00001854D-page 38

 2015-2016 Microchip Technology Inc.

8.5

Remote Wakeup Indicator

The remote wakeup indicator feature uses USB2_SUSP_IND as a side band signal to wake up the host when in USB2.0

suspend. This feature is enabled and disabled via the HUB_RESUME_INHIBIT configuration bit in the hub configuration

space register CFG3. The only way to control the bit is by configuration EEPROM, SMBus or internal ROM default set-

ting. The state is only modified during a power on reset, or hardware reset. No dynamic reconfiguring of this capability

is possible.

When HUB_RESUME_INHIBIT = ‘0’, Normal Resume Behavior per the USB 2.0 specification

When HUB_RESUME_INHIBIT = ‘1’, Modified Resume Behavior is enabled

For additional information, refer to the Microchip USB5734 Suspend Indicator application note on the Microchip.com

USB5734 product page.

8.6

Port Control Interface

Port power and over-current sense share the same pin (PRT_CTLx) for each port. These functions can be controlled

directly from the USB hub, or via the processor. Additionally, smart port controllers can be controlled via the I2C inter-

face.

The device can be configured into the following port control modes:

• Ganged Mode

• Combined Mode

Port connection in various modes are detailed in the following subsections.

8.6.1

PORT CONNECTION IN GANGED MODE

In this mode, one pin (GANG_PWR) is used to control port power and over-current sensing.

8.6.2

PORT CONNECTION IN COMBINED MODE

8.6.2.1

Port Power Control using USB Power Switch

When operating in combined mode, the device will have one port power control and over-current sense pin for each

downstream port. When disabling port power, the driver will actively drive a '0'. To avoid unnecessary power dissipation,

the pull-up resistor will be disabled at that time. When port power is enabled, it will disable the output driver and enable

the pull-up resistor, making it an open drain output. If there is an over-current situation, the USB Power Switch will assert

the open drain OCS signal. The Schmidt trigger input will recognize that as a low. The open drain output does not inter-

fere. The over-current sense filter handles the transient conditions such as low voltage while the device is powering up.

Note:

The USB2_SUSP_IND signal only indicates the USB2.0 state.

FIGURE 8-2:

PORT POWER CONTROL WITH USB POWER SWITCH

USB Power

Switch

50k

PRTPWR

OCS

Pull-Up Enable

USB

Device

FILTER

PRT_CTLx

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