AT43USB353M datasheet(81/95 Pages) ATMEL

81 / 95 page

AT43USB353M

3307B–USB–4/04

Port Power Switching

Gang Power Switching – One of the microcontroller GPIO pins, PWRN, must be pro-

grammed as an output to control the external switch such as the MIC2025-2. Switch

ON is requested by the USB Host through the SetPortFeature(PORT_POWER)

request. Switch OFF is executed upon receipt of a ClearPortFeature(PORT_POWER)

or upon detecting an overcurrent condition. The firmware clears the Power Control Bit.

Only if all of the Power Control Bits of ports 2 and 3 are cleared should the firmware de-

assert the PWRN pin.

Individual Power Switching – Two microcontroller GPIO pins, PWR2N and PWR3N,

must be assigned for each USB port to control the external switch such as the

MIC2026-2. Each of the Power Control Bits controls one PWRxN.

Multiple Ganged Overcurrent Protection – Overcurrent sensing is grouped physi-

cally into one or more gangs, but reported individually.

Figure 20 shows a simplified diagram of a power management circuit of an AT43USB353M

based hub design with global overcurrent protection and ganged power switching.

Figure 20. Port Power Management

Suspend and

Resume

The AT43USB353M enters suspend only when requested by the USB host through bus inac-

tivity for at least 3 ms. The USB hardware would detect this request, sets the GLB_SUSP bit of

SPRSR, Suspend/Resume Register, and interrupts the microcontroller if the interrupt is

enabled. The microcontroller should shut down any peripheral activity and enter the Power

Down mode by setting the SE and SM bits of MCUCR and then executes the SLEEP instruc-

tion. The USB hardware shuts off the oscillator and PLL.

CTL

FLG

OUT

SWITCH

AT43USB353M

GND

VCC

PWRN

OVCN

PORT2_POWER

PORT2_GND

PORT3_POWER

PORT3_GND

BUS_POWER

GND

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