AT43311 Просмотр технического описания (PDF) - Atmel Corporation

Номер в каталоге

Компоненты Описание

производитель

AT43311

USB Hub

Atmel Corporation 

AT43311

visual feedback. The default state of STAT[1:4] is inactive.

After a port is enabled AT43311 will assert the port’s

STAT[1:4].

Oscillator and Phase-Locked-Loop

To reduce EMI and power dissipation in the system, the

AT43311 on-chip oscillator is designed to operate with a 6

MHz external crystal. An on-chip PLL generates the high

frequency for the clock/data separator of the Serial Inter-

face Engine. In the suspended state, the oscillator circuitry

is turned off.

A 6 MHz parallel resonance quartz crystal with a load

capacitance of approximately 10 pF is recommended. If the

crystal load capacitor is larger, external capacitors added to

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. Oscillator and PLL Connection

Figure 2 shows how to properly connect the oscillator for

the AT43311. 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 1–Power Sup-

ply Connection.

To provide the best operating condition for the AT43311,

careful consideration of the power supply connections are

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 AT43311’s Hub Controller.

7

Share Link: