UM232R FTDI, Future Technology Devices International Ltd, UM232R Datasheet - Page 18

• Manufacturer Part Number: UM232R
• Description: MODULE USB-SER UART FT232 24-DIP
• Manufacturer: FTDI, Future Technology Devices International Ltd

Specifications of UM232R

• Main Purpose: Interface, USB 2.0 to UART (RS232) Bridge
• Embedded: No
• Utilized Ic / Part: FT232R
• Primary Attributes: Full Speed, Rates of 300 ~ 3 MBaud, Security ID Number
• Secondary Attributes: 6 ~ 48MHz Clock Generator Output, Royalty-Free Drivers
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: 768-1019

7.2 Self Powered Configuration
Figure 7.2 Self-Powered Configuration
Figure 7.2 illustrates the UM232R in a typical USB self powered configuration. In this case the link on
jumper J2 is removed, and an external supply is connected to the module VCC pins. Figure 7.2 illustrates a
self powered design which has a 3.5V – 5V supply.
A USB Self Powered device gets its power from its own power supply and does not draw current from the
USB bus. The basic rules for USB Self powered devices are as follows:
In order to meet requirement (i) the USB Power is used to control the RESET# Pin of the FT232R device.
When the USB Host or Hub is powered up the internal 1.5kΩ resistor on USBDP is pulled up to 3.3V, thus
identifying the devices as a full speed device to USB. When the USB Host or Hub Power is off, RESET# will
go low and the device will be held in reset. As RESET# is low, the internal 1.5kΩ resistor will not be pulled
up to 3.3V, so no current will be forced down USBDP via the 1.5kΩ pull-up resistor when the host or hub is
powered down.
To do this pin 14 (USB) is connected to PU2 and PU1 is connected to RST#. Failure to do this may cause
some USB host or hub controllers to power up erratically.
Note: When the FT232Ris in reset, the UART interface pins all go tri-state. These pins have internal 200kΩ
pull-up resistors to VCCIO, so they will gently pull high unless driven by some external logic.
© Copyright 2009 Future Technology Devices International Ltd
iii) A Self Powered Device can be used with any USB Host and both Bus and Self Powered USB Hub. In
ii) A Self Powered Device can use as much current as it likes during normal operation and USB suspend
i) A Self Powered device should not force current down the USB bus when the USB Host or Hub
Controller us powered down.
as it has its own power supply.
this case the power descriptor in the internal EEPROM should be programmed to a value of zero (self
powered).
Vcc = 3.3V – 5V
MCU
TXD
RXD
RTS#
CTS#
UM232R USB - Serial UART Development Module Incorporating Clock Generator
CTS#
GND
TXD
RXD
RTS# 3
10
12
7
1
5
J1
UM232R
1
J2
©
2
FTDI 2008
2
Document Reference No.: FT_000051
3
1
15
14
13
24
21
20
17
16
Clearance No.: FTDI# 125
VCC
USB
VCC
RST#
PU1
PU2
GND
Datasheet Version 1.04
Vcc = 3.5V – 5V
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