AT43310 データシートの表示（PDF） - Atmel Corporation

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AT43310

USB Hub

Atmel Corporation 

AT43310

pins OSC1 and OSC2 are recommended. The values for

these capacitors depends on the crystal and the layout of

the board, but typically are 33 pF at OSC1 and 47 pF at

OSC2. If the crystal used cannot tolerate the drive levels of

the oscillator, a series resistor between OSC2 and the crys-

tal pin may be used.

Figure 2 shows how to properly connect the oscillator for

the AT43310. Ceramic resonators are not recommended

due to the frequency stability required by the USB specifi-

cation (0.25%).

If desired, the clock can be externally sourced. To clock

externally, connect the clock source to the OSC1 pin, while

leaving the OSC2 pin floating. The switching level at the

OSC1 pin can be as low as 0.47V (see electrical specifica-

tions). A CMOS device is required to drive this pin to main-

tain good noise margins at the low switching level.

For proper operation of the PLL, see Figure 2-Ocscillator

and PLL Connection.

To provide the best operating condition for the AT43310,

careful consideration of the power supply connections are

Figure 2. Oscillator and PLL Connection

recommended. Use short, low impedance connections to

all power supply lines: VCC5, VCC3, VCCA, and VSS with 0.1

µF decoupling capacitors of high quality adjacent to the

device pins.

Descriptors

The Hub Controller supports the following standard USB

descriptors: Device, Configuration, Interface, and Endpoint

Descriptors, as well as the class specific Hub Descriptor.

All the required Standard Requests and Hub Class-Specific

Requests are supported by the AT43310’s Hub Controller.

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