UMFT221XA-01 FTDI, UMFT221XA-01 Datasheet - Page 9

• Manufacturer Part Number: UMFT221XA-01
• Description: Interface Development Tools USB to SPI/FT1248 Dev Mod for FT221X
• Manufacturer: FTDI
• Type: USB to SPIr

Specifications of UMFT221XA-01

• Rohs: yes
• Product: Development Modules
• Tool Is For Evaluation Of: FT221XQ
• Interface Type: USB, SPI
• Operating Supply Voltage: 3.3 V
• Dimensions: 34.7 mm x 12.2 mm x 2.2 mm
• Tradename: X-Chip

5.4
Figure 5.2 – Self-Powered Configuration
A self-powered configuration operates on the principle of drawing power from an external power supply,
as oppose to drawing power from the USB host. In this configuration no current is drawn from the USB
bus.
Figure 5.2 illustrates the UMFT221XA in a typical USB self-powered configuration. In this case the solder
links connection of JP1 is removed, which allows 5V power to be supplied to the module VCC pins from an
external source. VCCIO can to be powered from 3V3OUT or the VCC of an external source. (Note that
Figure 5.2 is for illustration only and that the pins do not actually go all the way through the PCB)
For a self-powered configuration it is necessary to prevent current from flowing back to the USB data
lines when the connected USB host or hub has powered down. To carry out this function the UMFT221XA
uses an on-board voltage divider network connected to the USB power bus and RESET# pin. This
operates on the principle that when no power is supplied to the VBUS line, the FT221X will automatically
be held in reset by a weak pull-down, when power is applied the voltage divider will apply a weak 3.3V
pull-up. Driving a level to the RESET# pin of the UMFT221XA will override the effect of this voltage
divider. When the FT221X is in reset the USB DP signal pull-up resistor connected to the data lines is
disconnected and no current can flow down the USB lines.
An example of interfacing the FT221X with a Microcontroller‟s SPI Master interface (in FT1248 1-bit
mode) is also illustrated in Figure 5.2. This example shows the wire configuration of the transfer and
handshake lines. This example also illustrates that a voltage other than 3.3V can be supplied to the
FT221X‟s IO port, this feature is described further and for bus powered mode in Section 5.6.
Alternatively both the FT221X‟s IO port and MCU can be powered from the 3V3OUT pin; this approach is
described in Section 5.5.
Vcc = 1.8V – 3.3V
Self Powered Configuration
MCU
VIO
SCLK
MISO
IO0
SS#
Solder Link JP1 - Open
Variable TTL
GND
Mode
Optionial
Optionial
Optionial
Optionial
Optionial
Optionial
Copyright © 2012 Future Technology Devices International Limited
IO0
IO1
IO2
IO3
IO4
IO5
IO6
Document Reference No.: FT_000518
Viewing pins thourgh the board
3V3OUT
VCCIO
from the top.
VBUS
VCC
Optionial
Solder Link JP2 - Open
IO7
Self Power
SCLK
MISO
SS#
Clearance No.: FTDI#
Mode
GND
9
UMFT221XA
Vcc = 5V
Version 1.1
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