USB7252P datasheet(39/64 Pages) MICROCHIP

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DS00003561A-page 39

USB7252P

8.2

Port Power Control

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.

8.2.1

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

PRT_CTLx function is assigned to programmable function pins (PFx) via configuration straps. Refer

to Section 3.3.4, PF[31:2] Configuration (CFG_STRAP[2:1]) for additional information.

Note:

The port power control for the USB 2.0 and USB 3.2 portions of a specific port can also be individually con-

trolled via the PortSplit function. Refer to Section 8.5, PortSplit for additional information.

Note:

An external power switch is the required implementation for Type-C ports due to the requirement that VBUS

on Type-C ports must be discharged to 0V when no device is attached to the port.

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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