USB5742 datasheet(27/48 Pages) MICROCHIP

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DS00002016G-page 27

USB5742

8.4

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.

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.

8.4.1

PORT CONNECTION IN GANGED MODE

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

8.4.2

PORT CONNECTION IN COMBINED MODE

8.4.2.1

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.

When the port is enabled, the PRT_CTLx pin input is constantly sampled. Overcurrent events can be detected in one

of two ways:

• Single, continuous low pulse (consecutive low samples over tocs_single), as shown in Figure 8-3.

• Two short low pulses within a rolling window (two groupings of 1 or more low samples over tocs_double), as shown

in Figure 8-4.

FIGURE 8-2:

PORT POWER CONTROL WITH USB POWER SWITCH

FIGURE 8-3:

SINGLE LOW PULSE OVERCURRENT DETECTION

USB Power

Switch

50k

PRTPWR

OCS

Pull‐Up Enable

USB

Device

FILTER

PRT_CTLx

IS VIL

tocs_single

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