GPIO4 datasheet(34/60 Pages) MICROCHIP

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USB5806

DS00002236D-page 34

 2016-2018 Microchip Technology Inc.

8.7.2.2

Port Power Control using Poly Fuse

When using the device with a poly fuse, there is no need for an output power control. To maintain consistency, the same

circuit will be used. 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 cathode 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.

TABLE 8-4:

OVERCURRENT LOCKOUT TIMER REGISTER

START_LOCKOUT_TIMER_REG

(30E1h)

Start Lockout Timer Register

BIT

Name

R/W

Description

7:0

START_LOCKOUT_TIMER_REG

R/W

The “start lockout timer” blocks an overcurrent event from

being detected immediately after port power is turned on.

Any overcurrent event within this timer value is ignored.

The timer can be incremented in 1ms steps. The default

value is 10ms (0Ah).

Note:

This register should never be set to 00h.

Note:

The USB 2.0 and USB 3.1 Gen 1 bPwrOn2PwrGood descriptors must be set to 0 when using poly-fuse

mode. Refer to the “Configuration Options for the USB58xx and USB59xx” Microchip application note for

details on how to change these values.

FIGURE 8-7:

PORT POWER CONTROL USING A POLY FUSE

PRT_CTLx

50k

PRTPWR

OCS

USB

Device

Pull-Up Enable

Poly Fuse

FILTER

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