USB7252CSLASHKDX datasheet(40/63 Pages) MICROCHIP

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DS00003852A-page 40

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2021 Microchip Technology Inc.

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.

8.3

CC Pin Orientation and Detection

The device provides CC1 and CC2 pins on all Type-C ports for cable plug orientation and detection of a USB Type-C

receptacle. The device also integrates a comparator and DAC circuit to implement Type-C attach and detach functions,

which supports up to eight programmable thresholds for attach detection between a UFP and DFP. When operating as

a UFP, the device supports detecting changes in the DFP’s advertised thresholds.

When operating as a DFP, the device implements current sources to advertise current charging capabilities on both CC

pins. By default, the CC pins advertise a 3A VBUS sourcing capability when operating in DFP mode. This may be recon-

figured to 1.5A or Default USB (500mA for USB2 DFP or 900mA for a USB3 DFP) via OTP, SMBus, or SPI configuration.

When a UFP connection is established, the current driven across the CC pins creates a voltage across the UFP’s Rd

pull-down that can be detected by the integrated CC comparator. When connected to an active cable, an alternative

pull-down, Ra, appears on the CC pin.

When operating as a UFP, the device applies an Rd pull-down on both CC lines and waits for a DFP connection from

the assertion of VBUS. The CC comparator is used to determine the advertised current charger capabilities supported

by the DFP.

VCONN is a 3V-5V supply used to power circuitry in the USB Type-C plug that is required to implement Electronically

Marked Cables and other VCONN Powered accessories. By default the DFP always sources VCONN when connected

to an active cable. The USB7252C requires the use of two external VCONN FETs. The device provides the enables for

these FETs, and can detect an over-current event (OCS) by monitoring the output voltage of the FET via the CC pins.

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.

FIGURE 8-3:

PORT POWER CONTROL USING A POLY FUSE

PRT_CTLx

50k

PRTPWR

OCS

USB

Device

Pull-Up Enable

Poly Fuse

FILTER

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