FT260 HID-CLASS USB TO UART/I2C BRIDGE IC
Version 1.1
Document No.: FT_001272 Clearance No.: FTDI#484
7 FT260 Power Configurations
Section 7.1 to section 7.4 illustrates possible USB power configurations for the FT260. Section 7.5 shows
the configuration for system pins about DCNF0, DCNF1, XRESETN and other system pins. Section 7.6
shows the power for programming eFUSE.
7.1 USB Bus Powered Configuration
Figure 7.1 Bus Powered Configuration
Figure 7.1 illustrates the FT260 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
i)
ii)
iii)
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) can use the
SUSPOUT_N function on the pin DIO7 as a power disable function and use it to keep the
current below 2.5mA on USB suspend.
iv)
v)
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 VCCIN pin is the power source for the FT260 and can directly connect to VBUS. When the I/O voltage
level is as +3.3V, users can directly connect VOUT3V3 to VCCIO without an external regulator. The
VBUS_DET pin is a 5V-tolerant input pin and can directly connect to VBUS without an on-board voltage
divider circuit. The power descriptors in the embedded eFUSE of the FT260 or in the external EEPROM
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 FT260 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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