UM232H FTDI, Future Technology Devices International Ltd, UM232H Datasheet - Page 17

• Manufacturer Part Number: UM232H
• Description: MOD EVAL USB - SERIAL - FT232H
• Manufacturer: FTDI, Future Technology Devices International Ltd

Specifications of UM232H

• Main Purpose: Interface, USB 2.0 to Serial FIFO Bridge
• Embedded: No
• Utilized Ic / Part: FT232H
• Primary Attributes: High Speed (480Mbps) Transceiver
• Secondary Attributes: LED Status Indicators
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: 768-1103

7.3 Self Powered Configuration
7.3.1 Self-Powered Configuration
Figure 7.3 : Self-Powered Configuration – 5V0 External Supply
Figure 7.3 illustrates the UM232H in a typical USB Self-Powered configuration. An external supply +5.0V is
connected to the module’s 5V0 pin. J2-2 (VIO) is also connected to J2-3 (3V3) to supply the VCCIO supply
from the on board regulator but a separate supply could have been used.
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 FT232H 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 J1-3 (USB) is connected to PU2 and PU1 is connected to J2-4 (RST#). Failure to do this may
cause some USB host or hub controllers to power up erratically.
Note: When the FT232H is 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.
Figure 7.3 is also an example of interfacing the FT232H to a Microcontroller (MCU) UART interface. This
example uses TXD and RXD for transmission and reception of data and RTS# / CTS# hardware
handshaking.
Optionally, RI# can be connected to another I/O pin on the MCU and could be used to wake up the USB
host controller from suspend mode. If the MCU is handling power management functions, then an ACBUS
pin can be configured as PWREN# and should be connected to an I/O pin of the MCU.
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 use 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).
5V or 3V3
MCU
© Copyright 2011 Future Technology Devices International Ltd
CTS#
RTS#
RXD
TXD
UM232H Single Channel USB Hi-Speed FT232H Development Module
with 3V3 I/O and running on +5V external supply:
16
J2-14
TXD
RXD
RTS#
CTS#
J2-1
PU2
PU1
3V3
VIO
Document Reference No.: FT_000367
USB
5V0
J1-1
J1-14
RST#
Clearance No.: FTDI# 198
5V
Datasheet Version 1.2