FT245BL/TR FTDI, FT245BL/TR Datasheet - Page 19

• Manufacturer Part Number: FT245BL/TR
• Description: IC, USB FIFO INTERFACE, 480MBPS, LQFP-32
• Manufacturer: FTDI

Specifications of FT245BL/TR

• Usb Type: FIFO
• Usb Version: 1.1, 2.0
• Data Rate: 480Mbps
• No. Of Ports: 2
• Supply Voltage Range: 4.35V To 5.25V
• Operating Temperature Range: 0°C To +70°C
• Digital Ic Case Style: LQFP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Figure 9
Bus Powered Circuit with 3.3V logic drive / supply voltage
Figure 9 shows how to configure the FT245BL to interface with a 3.3V logic device. In this example, a discrete
3.3V regulator is used to supply the 3.3V logic from the USB supply. VCCIO is connected to the output of the 3.3V
regulator, which in turn will cause the FIFO interface IO pins to drive out at 3.3V level. For USB bus powered circuits
some considerations have to be taken into account when selecting the regulator –
a) The regulator must be capable of sustaining its output voltage with an input voltage of 4.35 volts. A Low Drop Out
b) The quiescent current of the regulator must be low in order to meet the USB suspend total current requirement of
An example of a regulator family that meets these requirements is the MicroChip (Telcom) TC55 Series. These
devices can supply up to 250mA current and have a quiescent current of under 1uA.
In some cases, where only a small amount of current is required (< 5mA) , it may be possible to use the in-built
regulator of the FT245BL to supply the 3.3V without any other components being required. In this case, connect
VCCIO to the 3V3OUT pin of the FT245BL.
Note : It should be emphasised that the 3.3V supply for VCCIO in a bus powered design with a 3.3V logic interface
should come from an LDO which is supplied by USB bus, or from the 3V3OUT pin of the FT245BL, and not from any
other source.
(LDO) regulator must be selected.
<= 500uA during USB suspend.
Connector
USB "B"
DS245BL Version 1.6
1
2
3
4
10nF
Ferrite Bead
27R
© Future Technology Devices Intl. Ltd. 2005
27R
VCC
33nF
3.3v LDO Regulator
In
FT245BL USB FIFO ( USB - Parallel ) I.C.
Gnd
6
8
7
3v3OUT
Out
USB DM
USB DP
3
V
C
C
26
C
C
V
13
FT245BM
V
C
C
O
I
470R
3.3v Power to External
30
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C
C
A
V
0.1uF
Logic
0.1uF