AT43311 データシートの表示（PDF） - Atmel Corporation

部品番号

コンポーネント説明

メーカー

AT43311

USB Hub

Atmel Corporation 

Figure 1. Power Supply Connection

From upstream power regulator

VCC5

3V REG.

GND

VCC3

VREF

PWR

AT43311

5.5V

OVL

DP DM

STAT

5V POWER

SUPPLY

VCC5

VSS

To downstream device

Figure 1 illustrates an example of the power supply con-

nection for a AT43311 port.

Careful consideration must be taken to avoid large ground

current surges. There is the possibility that the upstream

device and the self powered device will be sourced from

different electrical power outlets which share no common

ground.

When designing the local power supply for the AT43311 or

a self powered device, local 5V power must be isolated.

This isolation can be achieved through a transformer or by

proper design of the switching power supply. The GND of

the Hub or device can then be safely connected to the

upstream ports ground line for proper operation of the USB

signals.

Even though the devices in a USB network share a com-

mon ground (VSS), the two 5V supply voltages of the

AT43311 based hub (the upstream’s bus power and the

local power) must not be connected under any condition.

Port [1:4] Power Control

Each port has signals for port power management and for

port status feedback (PWR[1:4], OVL[1:4], and STAT[1:4]).

The AT43311 monitors and switches the power to each

port individually.

PWR[1:4] are open drain outputs that control the power to

the downstream ports. The AT43311 asserts a low value to

ports PWR[1:4] to turn on the power to the port. During

power up, reset, and initialization of the Hub, PWR[1:4] is

in-active. PWR[1:4] is asserted when the Host instructs the

Hub to power the port through the SetPortPower = ON

command. Additionally PWR[1:4] is de-asserted by the Hub

when an overcurrent condition is detected at the port.

For proper operation of PWR[1:4], an external pull-up resis-

tor to VCC5 is required for PWR[1:4] pins. To control the

power to the port, any switch with a low voltage drop with

full power applied is acceptable. The AT43311 is designed

for a simple, low cost P-channel MOSFET to use as the

switch.

To detect a port overload, the AT43311 compares OVL[1:4]

to a common VREF defined by the designer.

OVL[1:4] should be attached to the power supply of the

respective downstream port. If OVL[1:4] drops below the

reference voltage VREF for more than 1 ms, the AT43311

treats the drop in voltage as a fault condition on the port’s

power supply. Upon this fault condition, the AT43311 sets

the port’s PORT_OVER_CURRENT status bit and the

port’s C_PORT_OVER_CURRENT bit. The AT43311 will

additionally shut off the power to the port by de-activating

the port’s PWR[1:4] signal.

The STAT[1:4] pins are not required by the USB specifica-

tion. STAT[1:4] provide feedback to the user whenever a

device is properly connected to the port. An LED and series

resistor connected to STAT[1:4] can be used to provide

6

AT43311

Share Link: