DS_FT2232D Datasheet, PDF (24/61 Pages) List of Unclassifed Manufacturers – Future Technology Devices International Ltd

Document No.: FT_000173
FT2232D DUAL USB TO SERIAL UART/FIFO IC Datasheet
Version 2.05
Clearance No.: FTDI# 127
Figure 6.4 Self Powered Circuit with 3.3V logic drive and IO supply voltage
Figure 6.4 is an example of a FT2232D USB self powered design with 3.3V interface. In this case
the VCCIOA and VCCIOB pins are supplied by an external 3.3V supply in order to make both of the
device‟s IO channels drive out at 3.3V logic level, thus allowing them to be connected to a 3.3V
MCU or other external logic. It is also possible to have one IO interface channel driving out at 5V
level, and the other at 3.3V level. In this case one of the VCCIO pins would be connected to 5V,
and the other connected to 3.3V. 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 FT2232D to supply the
3.3V without any other components being required. In this case, connect VCCIOA or VCCIOB to
the 3V3OUT pin of the FT2232D. Note that if the SI/WU pins are not being used they should be
pulled up to the same supply as their respective VCCIO pin.
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