E250D 水货版本  E250DDXHA2  版本下载

红景

普通会员
2005-11-10
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FT232BM USB UART ( USB - Serial) I.C.
VCC5V
27R
USB DM
RSTOUT#
8
FT232BM
USB DP
7
5
VCCI O
13
33nF 3v3OUT
6
GND
GND
AGN D
9 17 29
RESET#
4
VCC3V
VCC3V
PWRCTL
VC C
VC C
3 26
470R
AVCC
30
14
Figure 15 is an example of a USB self powered design with 3.3V interface. In this case VCCIO is supplied by an
external 3.3V supply in order to make the device IO pins drive out at 3.3V logic level, thus allowing it to be connected
to a 3.3V MCU or other external logic. A USB self powered design uses its own power supplies, and does not draw
any of its power from the USB bus. In such cases, no special care need be taken to meet the USB suspend current
(0.5 mA) as the device does not get its power from the USB port.
As with bus powered 3.3V interface designs, in some cases, where only a small amount of current is required (<5mA),
it may be possible to use the in-built regulator of the FT232BM to supply the 3.3V without any other components being
required. In this case, connect VCCIO to the 3v3OUT pin of the FT232BM.
Note that in this case PWRCTL is pulled up to VCCIO, not VCC.