MM232R Mini USB-Serial UART Development Module Datasheet Version 1.00

© Future Technology Devices International Ltd. 2005

Page 1

6. Module Configurations

6.1 Bus Powered Configuration

Figure 5 - Bus Powered Configuration

Figure 5 illustrates the MM232R in a typical USB bus powered design configuration. This is done by connecting pin 15

(USBPWR) to pin 14 (VCC50). Pin 3 (VCCIO), the supply to the FT232RQ’s UART and CBUS IO pins, is connected to

pin 2 (VCC). Doing this will make the UART and CBUS IO pins drive out at 5V levels.

A USB Bus Powered device gets its power from the USB bus. Basic rules for USB Bus power devices are as follows –

i) On plug-in to USB, the device must draw no more than 100mA.

ii) On USB Suspend the device must draw no more than 500μA.

iii) A Bus Powered High Power USB Device (one that draws more than 100mA) should use PWREN# to keep the

current below 100mA on plug-in and 500μA on USB suspend.

iv) A device that consumes more than 100mA can not be plugged into a USB Bus Powered Hub.

v) No device can draw more that 500mA from the USB Bus.

Figure 5 also illustrates interfacing the MM232R module to a microcontroller (MCU) UART interface. This example

uses TXD and RXD for transmission and reception of data, and RTS# / CTS# hardware handshaking. Also in this

example the 12MHz clock output on pin 9 is used to clock the MCU.

If the MCU is handling power management functions, then this can be done by connecting PWREN# to an I/O pin on

the MCU.

MM232R

© FTDI 2005

1

2

3

4

16 15 14 13

5

6

7

8

10

9

12

11

TXD

RXD

VCC

VCCIO

USBPWR

VCC50

RTS#

CTS#

CLK12M

GND

RTS#

TXD

CTS#

RXD

CLK_IN

I/O

MCU

VCC

PWREN#