DS_FT230X Datasheet, PDF (22/44 Pages) List of Unclassifed Manufacturers – Future Technology Devices International Ltd

6 USB Power Configurations
FT230X USB TO BASIC UART IC
Version 1.2
Document No.: FT_000566 Clearance No.: FTDI# 260
The following sections illustrate possible USB power configurations for the FT230X. The illustrations have
omitted pin numbers for ease of understanding since the pins differ between the FT230XS and FT230XQ
package options.
All USB power configurations illustrated apply to both package options for the FT230X device. Please refer
to Section 9 for the package option pin-out and signal descriptions.
6.1 USB Bus Powered Configuration
1
2
3
4
5
SHIELD
Ferrite
Bead
47pF
VCC
27R
27R
47pF
10nF
GND
100nF
GND
VCC
+ 4.7uF
GND
VCC
USBDM
USBDP
FT230X
RESET#
VCCIO
3V3OUT
100nF
GND
Figure 6.1 Bus Powered Configuration
Figure 6.1 Illustrates the FT230X 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 –
i) On plug-in to USB, the device should draw no more current than 100mA.
ii) In USB Suspend mode the device should draw no more than 2.5mA.
iii) 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.
iv) A device that consumes more than 100mA cannot be plugged into a USB bus powered hub.
v) No device can draw more than 500mA from the USB bus.
The power descriptors in the internal MTP memory of the FT230X 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 FT230X 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 # MI0805K601R-10.
Copyright © 2013 Future Technology Devices International Limited
22