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DS00002774G-page 21

USB4712

8.0

FUNCTIONAL DESCRIPTIONS

This section details various USB4712 functions, including:

• Downstream Battery Charging

• Auto-FlexConnect

• USB to GPIO Bridging

• USB to SMBus/I2C Bridging

• USB to SPI Bridging

• USB to UART Bridging

• Link Power Management (LPM)

• Port Power Control

• Resets

8.1

Downstream Battery Charging

The device can be configured by an OEM to have the downstream port support battery charging. The hub’s role in bat-

tery charging is to provide acknowledgment to a device’s query as to whether the hub system supports USB battery

charging. The hub silicon does not provide any current or power FETs or any additional circuitry to actually charge the

device. Those components must be provided externally by the OEM.

If the OEM provides an external supply capable of supplying current per the battery charging specification, the hub can

be configured to indicate the presence of such a supply from the device. This indication, via a handshake on the D+ and

D- at the start of the connection with the device, is on a per port basis.

For detailed information on utilizing the USB4712 battery charging feature, refer to the application note “USB Battery

Charging with Microchip USB4712 Hub

”, which can be found on the Microchip USB4712 product page at www.micro-

chip.com/USB4712.

8.2

Auto-FlexConnect

The USB4712 employs unique Auto-FlexConnect USB functionality, whereby the downstream port can be reconfigured

to become an upstream port, allowing the host or master capability to be switched between ports. This port/host

becomes the master of the new USB bus, while the other port can connect as USB device. The Auto-FlexConnect capa-

bility enables the host/device swap to take place automatically. When the USB4712 detects a USB device disconnect,

the Auto-FlexConnect feature attempts to detect a newly connected host on the downstream port. FlexConnect acti-

vates if a new host on the downstream port is detected. If a new host is not detected, the hub remains in the default

“unflexed” state.

FlexConnect can also be manually enabled through any of the following three methods. (See Note 8-1.)

• SMBus Control: An embedded SMBus master can manually control the state of the FlexConnect feature through

basic write/read operations.

• USB Command: FlexConnect can be manually initiated via a special USB command directed to the hub’s internal

Hub Feature Controller device.

• Direct Pin Control: Any available GPIO pin on the hub can be assigned the role of a manual FlexConnect control

pin.

FIGURE 8-1:

BATTERY CHARGING EXTERNAL POWER SUPPLY

SOC

VBUS[n]

PRT_CTL1

INT

SCL

SDA

Microchip

Hub

DC Power