FT4222HQ-C-R datasheet(31/49 Pages) FTDI

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FT4222H USB2.0 TO QUADSPI/I2C BRIDGE IC

1.3

Document No.: FT_001011 Clearance No.: FTDI#405

FT4222H Configurations

The following sections illustrate possible USB power configurations for the FT4222H.

7.1

USB Bus Powered Configuration

Figure 7.1 Bus Powered Configuration

Figure 7.1 illustrates the FT4222H in a typical USB2.0 bus powered design configuration. A USB bus

powered device gets its power from the USB bus. Basic rules for USB bus powered devices are as follows

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) can use

SUSP_OUT(pin-15) as a power disable function and use it to keep the current below 2.5mA

on USB suspend.

iv)

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.

The power descriptors in the internal OTP memory of the FT4222H 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 FT4222H

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 Steward (www.steward.com), for example Laird Technologies Part # MI0805K400R-10.

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