UM232R FTDI, UM232R Datasheet - Page 16

• Manufacturer Part Number: UM232R
• Description: Interface Modules & Development Tools USB to Serial UART Dev Mod for FT232R
• Manufacturer: FTDI
• Type: Development Moduler

Specifications of UM232R

• Interface Type: USB, Serial, UART
• Data Bus Width: Serial
• Operating Supply Voltage: 1.8 V to 5.25 V
• Product: Interface Modules
• Supported Devices: FT232R
• Svhc: No SVHC (18-Jun-2010)
• Development Tool Type: Development Kit
• Kit Features: Single Chip USB To Asynchronous Serial Data Transfer Interface, Auto Transmit Buffer
• Rohs Compliant: Yes
• Supported Families: FT232RL
• Features: Single Chip USB To Asynchronous Serial Data Transfer Interface, Auto Transmit Buffer Control
• Tool / Board Applications: USB To
• For Use With/related Products: FT232R
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Figure 7 - USB Bus Powered 3.3V Logic Drive
Figure 7 shows a configuration where a jumper switch is used to allow the FT232R to be interfaced with a 3.3V or 5V
logic devices. The FT232R’s VCCIO pin is either supplied with 5V from the USB bus (connect together pins 2 and 3
on J1), or with 3.3V from the FT232R’s 3V3OUT pin (connect together pins 1 and 2 on J1 as shown). The supply to
UM232R’s 3V3 pin can also be used to supply up to 50mA to external logic.
Please note the following in relation to bus powered designs of this type -
i)
ii) The maximum current source from USB Bus during normal operation should not exceed 100mA, otherwise a bus
Another possible configuration would be to use a discrete low dropout regulator which is supplied by the 5V on the
USB bus to supply 2.8V - 1.8V to the VIO pin and to the external logic. VCC would be supplied with the 5V from the
USB bus (available from the module’s USB pin). With VIO connected to the output of the low dropout regulator, would
in turn will cause the FT232R I/O pins to drive out at 2.8V - 1.8V logic levels.
For USB bus powered circuits some considerations have to be taken into account when selecting the regulator –
iii) The regulator must be capable of sustaining its output voltage with an input voltage of 4.35V. A Low Drop Out
iv) 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 of devices
(www.microchip.com). These devices can supply up to 250mA current and have a quiescent current of under 1μA.
UM232R USB-Serial UART Development Module Datasheet Version 1.02
PWREN# or SLEEP# signals should be used to power down external logic during USB suspend mode, in order to
comply with the limit of 500μA. If this is not possible, use the configuration shown in
powered design with power switching
(L.D.O.) regulator must be selected.
<= 500μA during USB suspend.
6.4 USB Bus Powered with 3.3V Logic Drive / IO Supply Voltage
(Section
12
1
6.3) should be used.
J1
1 2 3
J2
24
13
© Future Technology Devices International Ltd. 2005
Section
6.3.