FT200XD Datasheet, PDF (19/42 Pages) Future Technology Devices International Ltd. – FT200XD USB I2C SLAVE IC Datasheet Version 1.3

7 USB Power Configurations
FT200XD USB I2C SLAVE IC Datasheet
Version 1.3
Document No.: FT_000628 Clearance No.: FTDI# 265
The following sections illustrate possible USB power configurations for the FT200XD.
7.1 USB Bus Powered Configuration
5
SHIELD
1
2
3
4
47pF
Ferrite
Bead
VCC
27R
27R
10nF
47pF
GND
100nF
GND
VCC
+
4.7uF
GND
VCC
USBDM
USBDP
FT200XD
RESET#
VCCIO
3V3OUT
100nF
GND
Figure 7.1 Bus Powered Configuration
Figure 7.1Illustrates the FT200XD 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 must draw no more current than 100mA.
ii)
In USB Suspend mode the device must draw no more than 2.5mA.
iii)
A bus powered high power USB device (one that draws more than 100mA) should use the
CBUS pins configured as PWREN# and use it to keep the current below 100mA on plug-in and
2.5mA on USB suspend. Using the CBUS pin for PWREN# prevents the FT200XD from
indicating a USB Battery Charger is connected.
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 FT200XDmustbe 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 FT200XD
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.
Note: If using PWREN# (available using the CBUS) the pin must be pulled to VCCIO using a 10kΩ
resistor.
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