UMFT231XE-01 FTDI, UMFT231XE-01 Datasheet - Page 10

• Manufacturer Part Number: UMFT231XE-01
• Description: Interface Development Tools USB to UART DIP Dev. Module
• Manufacturer: FTDI
• Type: USB to UARTr
• Series: FT231Xr

Specifications of UMFT231XE-01

• Rohs: yes
• Product: Development Modules
• Tool Is For Evaluation Of: FT231XQ
• Interface Type: I2C, UART, USB
• Operating Supply Voltage: 3.3 V
• Description/function: USB to UART evaluation module
• Dimensions: 29.02 mm x 19.24 mm x 9.2 mm
• Operating Supply Current: 1 A
• Factory Pack Quantity: 25
• For Use With: FT231XQ

5.4
Figure 5.3 – Bus Powered with Power Switching Configuration
USB bus powered mode is introduced in Section 5.2. This section describes how to use bus-powered
mode with a power switch.
USB bus powered circuits are required by USB compliance standards to consume less than 2.5mA (and
less than 100mA when not enumerated and not suspended) when connected to a host or hub when in
USB suspend mode. The PWREN# CBUS function can be used to remove power from external circuitry
whenever the FT231X is not enumerated.
To implement a power switch using PWREN#, configure a P-Channel Power MOSFET to have a soft start
by fitting a 10K pull-up, a 1K series resistor and a 100nF cap as shown in Figure 5.3.
Connecting the source of the P-Channel MOSFET to 3V3OUT instead of VBUS can allow external logic to
source 3.3V power from the FT231X without breaking USB compliancy. In this setup it is important that
the VCCIO is not sourced from the drain of this MOSFET, this is because the power used to drive the gate
of this transistor is sourced from VCCIO. VCCIO should be connected directly to 3V3OUT for this setup to
function effectively. It is also important that the external logic must and IO core of the FT231X must not
draw more that 50mA, this is because the current limit of the internal 3.3V regulator is 50mA.
USB Bus Powered with Power Switching Configuration
MCU
VCC
5V
TXD
RXD
RTS#
CTS#
Jumper JP1 - Closed
3.3V TTL Mode
GND
Self-Sorced
TXD
RXD
RTS#
CTS#
Copyright © 2012 Future Technology Devices International Limited
3V3OUT
VCCIO
Document Reference No.: FT_000652
VBUS
VCC
Jumper JP2 - Closed
CBUSx
PWREN#
Bus Powered
10K
Mode
GND
P-Channel Power
1K
MOSFET
s
g
Clearance No.: FTDI#
d
10
Circuit
Start
Soft
UMFT231XE
0.1uF
Version 1.0
0.1uF
294