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FT245BQ 参数 Datasheet PDF下载

FT245BQ图片预览
型号: FT245BQ
PDF下载: 下载PDF文件 查看货源
内容描述: USB FIFO ( USB - 并行) I.C. [USB FIFO ( USB - Parallel ) I.C.]
分类和应用: 先进先出芯片
文件页数/大小: 24 页 / 557 K
品牌: FTDI [ FUTURE TECHNOLOGY DEVICES INTERNATIONAL LTD. ]
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FT245BQ USB FIFO ( USB - Parallel ) I.C.  
7.3 USB Bus Powered and Self Powered Configuration  
Figure 7  
USB Bus Powered Configuration  
Ferrite Bead  
470R  
USB "B"  
Connector  
VCC  
1
27R  
30  
2
3
3
26  
13  
0.1uF  
V
C
C
V
C
C
V
A
V
C
C
27R  
4
C
C
I
6
10nF  
3v3OUT  
O
33nF  
8
7
USB DM  
USB DP  
FT245BQ  
1k5  
5
RSTOUT#  
RESET#  
VCC  
VCC  
4
A
G
N
D
G
N
D
G
N
D
+
10uF  
9
17  
29  
0.1uF  
0.1uF  
Decoupling Capacitors  
Figure 7 illustrates a typical USB bus powered configuration. A USB Bus Powered device gets its power from the USB  
bus. Basic rules for USB Bus power devices are as follows –  
a) On plug-in, the device must draw no more than 100mA  
b) On USB Suspend the device must draw no more than 500uA.  
c) A Bus Powered High Power Device (one that draws more than 100mA) should use the PWREN# pin to keep the  
current below 100mA on plug-in and 500uA on USB suspend.  
d) A device that consumes more than 100mA can not be plugged into a USB Bus Powered Hub  
e) No device can draw more that 500mA from the USB Bus.  
The power descriptor in the EEPROM should be programmed to match the current draw of the device.  
A Ferrite Bead is connected in series with USB power to prevent noise from the device and associated circuitry (EMI)  
being radiated down the USB cable to the Host. The value of the Ferrite Bead depends on the total current required by  
the circuit – a suitable range of Ferrite Beads is available from Steward (www.steward.com) for example Steward Part  
# MI0805K400R-00 also available as DigiKey Part # 240-1035-1.  
DS245BQ Version 1.7  
© Future Technology Devices Intl. Ltd. 2005  
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