USB7006SLASHKDX datasheet(33/56 Pages) MICROCHIP

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DS00003715B-page 33

USB7006

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.

8.2.2

PORT POWER CONTROL USING POLY FUSE

When using the device with a poly fuse, there is no need for an output power control. A single port power control and

over-current sense for each downstream port is still used from the Hub's perspective. When disabling port power, the

driver will actively drive a '0'. This will have no effect as the external diode will isolate pin from the load. When port power

is enabled, it will disable the output driver and enable the pull-up resistor. This means that the pull-up resistor is providing

3.3 volts to the anode of the diode. If there is an over-current situation, the poly fuse will open. This will cause the cath-

ode of the diode to go to 0 volts. The anode of the diode will be at 0.7 volts, and the Schmidt trigger input will register

this as a low resulting in an over-current detection. The open drain output does not interfere.

Note:

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

to Section 3.3.4, PF[31:3] Configuration (CFG_STRAP[2:1]) 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

Note:

Type-C ports may not utilize a Poly-Fuse port power implementation due to the requirements that VBUS

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

USB Power

Switch

50k

PRTPWR

OCS

Pull‐Up Enable

USB

Device

FILTER

PRT_CTLx

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