FT2232D datasheet(21/61 Pages) ETC2

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Document No.: FT_000173

FT2232D DUAL USB TO SERIAL UART

/FIFO IC Datasheet

Version 2.05

Clearance No.: FTDI# 127

6 USB Power Configurations

The following sections illustrate possible USB power configurations for the FT2232D.

6.0 USB Bus Powered Configuration

Figure 6.1 Bus Powered Configuration

Figure 6.1 illustrates the FT2232D in a typical USB bus powered configuration. A USB Bus

Powered device gets its power from the USB bus. Basic rules for USB Bus power devices are as

follows:-

a) On plug-in, the device must draw no more than 100mA

b) On USB Suspend the device must draw no more than 500μA.

c) A High Power USB Bus Powered Device (one that draws more than 100mA) should use the

PWREN# pin to keep the current below 100mA on plug-in and 500μA on USB suspend.

d) A device that consumes more than 100mA cannot be plugged into a USB Bus Powered Hub

e) No device can draw more that 500mA from the USB Bus.

The power descriptor in the EEPROM should be programmed to match the current draw required by the

device. A Ferrite Bead is connected in series with USB power to prevent noise from the device and

associated circuitry (EMI) being radiated down the USB cable to the Host. The value of the Ferrite Bead

depends on the total current required by the circuit - a suitable range of Ferrite Beads is available from

Steward (www.steward.com) for example Steward Part # MI0805K400R-00 also available from DigiKey,

Part # 240-1035-1.

FT2232D Datasheet(PDF) 21 Page - List of Unclassifed Manufacturers