UMFT221XA-01 FTDI, UMFT221XA-01 Datasheet - Page 10

• 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

5.5
Figure 5.3 – Bus Powered with Power Switching Configuration
USB bus powered mode is introduced in Section5.3 This section describes how to use bus-powered mode
with a power switch.
USB bus powered circuits are required by USB compliance standards to consume less than 2.5mA (and
less than 100mA when not enumerated and not suspended) when connected to a host or hub when in
USB suspend mode. The PWREN# CBUS function can be used to remove power from external circuitry
whenever the FT221X is not enumerated. (Note: It is impossible to be in suspended mode when
enumerated.) (Note that Figure 5.3 is for illustration only and that the pins do not actually go all the way
through the PCB)
To implement a power switch using PWREN#, configure a P-Channel Power MOSFET to have a soft start
by fitting a 10K pull-up, a 1K series resistor and a 100nF cap as shown in Figure 5.3.
Connecting the source of the P-Channel MOSFET to 3V3OUT instead of VBUS can allow external logic to
source 3.3V power from the FT221X without breaking USB compliancy. In this setup it is important that
the VCCIO is not sourced from the drain of this MOSFET, this is because the power used to drive the gate
of this transistor is sourced from VCCIO. VCCIO should be connected directly to 3V3OUT for this setup to
function effectively. It is also important that the external logic must and IO core of the FT221X must not
draw more that 50mA, this is because the current limit of the internal 3.3V regulator is 50mA.
MCU
USB Bus Powered with Power Switching Configuration
VCC
SCLK
MISO
IO0
SS#
Solder Link JP1 - Closed
3.3V TTL Mode
GND
Self-Sorced
Optionial
Optionial
Optionial
Optionial
Optionial
Optionial
IO0
IO1
IO2
IO3
IO4
IO5
IO6
Viewing pins thourgh the board
3V3OUT
Copyright © 2012 Future Technology Devices International Limited
VCCIO
from the top.
Document Reference No.: FT_000518
VBUS
VCC
Optionial
Solder Link JP2 - Closed
CBUS3
PWREN#
IO7
Bus Powered
SCLK
MISO
SS#
Mode
10K
P-Channel Power
GND
1K
MOSFET
Clearance No.: FTDI#
s
g
10
UMFT221XA
d
Version 1.1
Circuit
Start
Soft
0.1uF
0.1uF
268