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參數資料
| 型號： | FT245BM |
| 廠商： | Future Technology Devices International Ltd |
| 元件分類： | 微控制器/微處理器 |
| 中文描述： | SPECIALTY MICROPROCESSOR CIRCUIT, PQFP32 |
| 封裝： | 7 X 7 MM, 0.80 MM PITCH, LQFP-32 |
| 文件頁數： | 14/24頁 |
| 文件大?。?/td> | 995K |
| 代理商： | FT245BM |
DS245B Version 1.7
Future Technology Devices Intl. Ltd. 2005
Page 21 of 24
FT245BM USB FIFO ( USB - Parallel ) I.C.
Figure 11
Bus Powered Circuit with Power Control
USB Bus powered circuits need to be able to power down in USB suspend mode in order to meet the <= 500uA total
suspend current requirement (including external logic). Some external logic can power itself down into a low current
state by monitoring the PWREN# pin. For external logic that cannot power itself down in that way, the FT245BM
provides a simple but effective way of turning off power to external circuitry during USB suspend.
Figure 11 shows how to use a discrete P-Channel Logic Level MOSFET to control the power to external logic
circuits. A suitable device could be a Fairchild NDT456P, or International Rectier IRLML6402, or equivalent. It is
recommended that a “soft start” circuit consisting of a 1K series resistor and a 0.1 uF capacitor are used to limit the
current surge when the MOSFET turns on. Without the soft start circuit there is a danger that the transient power
surge of the MOSFET turning on will reset the FT245BM, or the USB host / hub controller. The values used here
allow attached circuitry to power up with a slew rate of ~12.5 V per millisecond, in other words the output voltage will
transition from GND to 5 V in approximately 400 microseconds.
Alternatively, a dedicated power switch I.C. with inbuilt “soft-start” can be used instead of a MOSFET. A suitable
power switch i.c. for such an application would be a Micrel (www.micrel.com) MIC2025-2BM or equivalent.
Please note the following points in connection with power controlled designs –
a) The logic to be controlled must have its own reset circuitry so that it will automatically reset itself when power is re-
applied on coming out of suspend.
b) Set the Pull-down on Suspend option in the FT245BM’s EEPROM.
c) For USB high-power bus powered device (one that consumes greater than 100 mA, and up to 500 mA of current
from the USB bus), the power consumption of the device should be set in the max power eld in the EEPROM.
A high-power bus powered device must use this descriptor in the EEPROM to inform the system of its power
requirements.
d) For 3.3V power controlled circuits VCCIO must not be powered down with the external circuitry (PWREN# gets
its VCC supply from VCCIO). Either connect the power switch between the output of the 3.3V regulator and the
external 3.3V logic OR if appropriate power VCCIO from the 3v3OUT pin of the FT245BM.
Ferrite Bead
470R
0.1uF
VCC
27R
USB "B"
Connector
27R
USB DM
8
FT245BM
USB DP
7
V
C
V
C
V
C
I
O
3
26
13
1
2
3
4
33nF
3v3OUT
6
A
V
C
30
10nF
PWREN#
15
0.1uF
Switched 5v Power to
External Logic
P-Channel Power
MOSFET
s
g
d
0.1uF
1K
Soft Start
Circuit
OBSOLETE
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相關代理商/技術參數 |
參數描述 |
|---|---|
| FT245BM-TRAY | 功能描述:USB 接口集成電路 Obsolete See FT245RL RoHS:否 制造商:Cypress Semiconductor 產品:USB 2.0 數據速率: 接口類型:SPI 工作電源電壓:3.15 V to 3.45 V 工作電源電流: 最大工作溫度:+ 85 C 安裝風格:SMD/SMT 封裝 / 箱體:WLCSP-20 |
| FT245BQ | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:FT245BQ USB FIFO ( USB - Parallel ) I.C. |
| FT245BQ-REEL | 功能描述:USB 接口集成電路 USB to Parallel FIFO IC QFN-32 RoHS:否 制造商:Cypress Semiconductor 產品:USB 2.0 數據速率: 接口類型:SPI 工作電源電壓:3.15 V to 3.45 V 工作電源電流: 最大工作溫度:+ 85 C 安裝風格:SMD/SMT 封裝 / 箱體:WLCSP-20 |
| FT245R | 制造商:FTDI 制造商全稱:FTDI 功能描述:USB FIFO I.C. Incorporating FTDIChip-ID⑩ Security Dongle |
| FT245R_10 | 制造商:FTDI 制造商全稱:FTDI 功能描述:USB FIFO IC - Single chip USB to parallel FIFO bidirectional data transfer interface |
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