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參數(shù)資料
| 型號(hào)： | AT43312 |
| 廠商： | Atmel Corp. |
| 英文描述： | Self- and Bus- Powered USB Hub Controller |
| 中文描述： | 自和總線供電的USB集線器控制器 |
| 文件頁數(shù)： | 8/21頁 |
| 文件大?。?/td> | 157K |
| 代理商： | AT43312 |
AT43312
8
Oscillator and Phase-Locked-Loop
All the clock signals required to run the AT43311 are
derived from an on-chip oscillator. To reduce EMI and
power dissipation in the system, the oscillator is designed
to operate with a 6 MHz crystal. An on-chip PLL generates
the high-frequency for the clock/data separator of the Serial
Interface Engine. In the suspended state, the oscillator cir-
cuitry is turned off. To assure quick startup, a crystal with a
high Q, or low ESR, should be used. To meet the USB hub
frequency accuracy and stability requirements for hubs, the
crystal should have an accuracy and stability of better than
500 PPM. Even though the oscillator circuit would work
with a ceramic resonator, its use is not recommended
because a resonator would not have the frequency accu-
racy and stability.
A 6 MHz series resonance quartz crystal with a load capac-
itance of approximately 10 pF is recommended. If the crys-
tal recommended load capacitor is larger, external capaci-
tors added to pins OSC1 and OSC2 are recommend. The
values for these capacitors depends on the crystal and the
layout of the board, but a starting value of 22 pF at OSC1
and OSC2 should work fine in most cases. If the crystal
used cannot tolerate the drive levels of the oscillator, a
series resistor between OSC2 and the crystal pin is recom-
mended.
The clock can also be externally sourced. In this case, con-
nect the clock source to the OSC1 pin, while leaving OSC2
pin floating. The switching level at the OSC1 pin can be as
low as 0.47V (see “Oscillator Signals: OSC1, OSC2” table
on page 18) and a CMOS device is required to drive this
pin to maintain good noise margins at the low switching
level.
Figure 4.
Oscillator and PLL Connections
For proper operation of the PLL, an external RC filter con-
sisting of a series RC network of 100
and 10 nF in paral-
lel with a 2 nF capacitor must be connected from the LFT
pin to V
SS
.
To provide the best operating condition for the AT43312,
careful consideration of the power supply connections are
recommended. Use short, low impedance connections to
all power supply lines: V
CC
, V
CCA
and V
SS
. Use sufficient
decoupling capacitors to reduce noise: 0.1
μ
F decoupling
high-quality capacitors, soldered as close as possible to
the package pins are recommended.
OSC2
AT43312
OSC1
LFT
U1
C1
22pF
C2
22pF
Y1
6.000 MHz
C4
2nF
C3
10nF
R1
100
R2
100
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| AT43320 | Full-speed USB Hub/Function Microcontroller |
| AT43DK301 | Low-Cost USB Hub Development Kit |
| AT43DK312A | USB Hub Development Kit |
| AT43USB320A-AC | Full-speed USB Microcontroller with an Embedded Hub |
| AT43USB321 | Full-speed USB Hub/Function Microcontroller |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| AT43312(32DIP) | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:BUS CONTROLLER |
| AT43312(32SOIC) | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:BUS CONTROLLER |
| AT43312A | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:AT43312A [Updated 7/03. 27 Pages] |
| AT43312A_06 | 制造商:ATMEL 制造商全稱:ATMEL Corporation 功能描述:Self- and Bus-Bus-powered USB Hub Controller |
| AT43312A-6AC | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:BUS CONTROLLER |
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