USB2640 datasheet(19/60 Pages) MICROCHIP

номер детали	USB2640

подробное описание детали	Ultra Fast USB 2.0 Multi-Format Flash Media Controller/USB Hub Combo

PDF	60 Pages

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производитель	MICROCHIP [Microchip Technology]

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DS00001947C-page 19

USB2640/USB2641

6.3.2

PORT POWER CONTROL USING A POLY FUSE

When using the USB2640/USB2641 with a poly fuse, an external diode must be used (See Figure 6-2). When disabling

port power, the USB2640/USB2641 will drive a '0'. This procedure will have no effect since the external diode will isolate

the pin from the load. When port power is enabled, the USB2640/USB2641 output driver is disabled, and the pull-up

resistor is enabled which creates an open drain output. The open drain output condition 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 causing the

cathode of the diode to go to 0 volts. The anode of the diode will be at 0.7 volt, and the Schmitt trigger input will register

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

FIGURE 6-1:

PORT POWER CONTROL WITH USB POWER SWITCH

USB2640/

USB2641

USB Power

Switch

USB

Device

PRTCTL3

OCS

USB Power

Switch

USB

Device

PRTCTL2

OCS

USB2640 датащи(PDF) 19 Page - Microchip Technology