FT245R Future Technology Devices Intl Ltd., FT245R Datasheet - Page 18

• Manufacturer Part Number: FT245R
• Manufacturer: Future Technology Devices Intl Ltd.

7. Device Configurations
Please note that pin numbers on the FT245R chip in this section have deliberately been left out as they vary between
the FT245RL and FT245RQ versions of the device. All of these configurations apply to both package options for the
FT245R device. Please refer to
Figure 11 - Bus Powered Configuration
Figure 11 illustrates the FT245R 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)
ii) On USB Suspend the device must draw no more than 500μA.
iii) A Bus Powered High Power USB Device (one that draws more than 100mA) should use the PWREN# pin to keep
iv) A device that consumes more than 100mA can not be plugged into a USB Bus Powered Hub
v) No device can draw more that 500mA from the USB Bus.
The power descriptor in the internal EEPROM should be programmed to match the current draw of 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.
FT245R USB UART I.C. Datasheet Version 1.02
On plug-in to USB, the device must draw no more than 100mA.
the current below 100mA on plug-in and 500μA on USB suspend.
7.1 Bus Powered Configuration
SHIELD
5
1
2
3
4
10nF
100nF
GND
Section 4
+
Ferrite
Bead
4.7uF
GND
for the package option pin-out and signal descriptions.
+
Vcc
Vcc
GND
100nF
© Future Technology Devices International Ltd. 2005
VCC
USBDM
USBDP
3V3OUT
VCCIO
RESET#
OSCI
OSCO
NC
NC
A
G
N
D
FT245R
G
N
D
G
N
D
GND
G
N
D
T
E
S
T
PWREN#
RXF#
TXE#
WR#
RD#
D0
D1
D2
D3
D4
D5
D6
D7