FT231XQ-T FTDI, FT231XQ-T Datasheet - Page 22

• Manufacturer Part Number: FT231XQ-T
• Description: USB Interface IC USB to Full Serial UART IC QFN-20
• Manufacturer: FTDI

Specifications of FT231XQ-T

• Rohs: yes
• Tradename: X-Chip

6
The following sections illustrate possible USB power configurations for the FT231X. The illustrations have
omitted pin numbers for ease of understanding since the pins differ between the FT231XS and FT231XQ
package options.
All USB power configurations illustrated apply to both package options for the FT231X device. Please refer
to Section 9 for the package option pin-out and signal descriptions.
6.1 USB Bus Powered Configuration
Figure 6.1 Bus Powered Configuration
Figure 6.1 Illustrates the FT231X in a typical USB bus powered design configuration. A USB bus powered
device gets its power from the USB bus. Basic rules for USB bus power devices are as follows –
The power descriptors in the internal MTP memory of the FT231X should be programmed to match the
current drawn by the device.
A ferrite bead is connected in series with the USB power supply to reduce EMI noise from the FT231X and
associated circuitry being radiated down the USB cable to the USB host. The value of the Ferrite Bead
depends on the total current drawn by the application. A suitable range of Ferrite Beads is available from
Laird Technologies (http://www.lairdtech.com), for example Laird Technologies Part # MI0805K400R-10.
Note: If using PWREN# (available using the CBUS) the pin should be pulled to VCCIO using a 10kΩ
resistor.
i)
ii)
iii)
iv)
v)
USB Power Configurations
SHIELD
On plug-in to USB, the device should draw no more current than 100mA.
In USB Suspend mode the device should draw no more than 2.5mA.
A bus powered high power USB device (one that draws more than 100mA) should use one of
the CBUS pins configured as PWREN# and use it to keep the current below 100mA on plug-in
and 2.5mA on USB suspend.
A device that consumes more than 100mA cannot be plugged into a USB bus powered hub.
No device can draw more than 500mA from the USB bus.
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Copyright © 2013 Future Technology Devices International Limited
1
2
3
4
100nF
GND
10nF
47pF
Ferrite
Bead
VCC
FT231X USB TO FULL HANDSHAKE UART IC
+
GND
GND
4.7uF
47pF
VCC
Document No.: FT_000565 Clearance No.:
GND
27R
27R
100nF
USBDM
USBDP
VCC
RESET#
VCCIO
3V3OUT
FT231X
Datasheet
Version 1.2
FTDI# 261
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