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FT232BM Designers Guide

DG232 Version 2.0 © Future Technology Devices Intl. Ltd. 2002/2003 of 16


Version 2.0 Introduction

Welcome to the FT232BM Designer’s Guide. The Designers Guide includes printouts of a number of FT232BM

reference schematics and explanations of the key points of each schematic. These are intended to be used in

conjunction with the FT232BM data sheet, the current version of which should also be downloaded from the

FTDI web site.

The schematic les are downloadable separately as a ZIP archive which contains the schematics both in

OrCAD SDT 16-bit DOS format and in OrCAD Capture for Windows 32-bit format.

The OrCAD SDT 16-bit DOS format schematics are readable by OrCAD SDT version 3.2 and above. These

consist of les with the following extensions –

• .sch = OrCAD 16-bit DOS binary schematic le

• .lib = OrCAD 16-bit DOS binary component library le

• .src = OrCAD DOS library source ( text ) le

The OrCAD Capture for Windows schematics are readable by OrCAD Capture version 7.2 and above. These

consist of a le with a .dsn extension.

Notes for Protel users

OrCAD 16-bit DOS schematics can be imported into Protel schematic capture for Windows. Before reading in

the schematic ( .sch ) le, create a Protel library rst by reading in the OrCAD library source ( .src ) le and

save it in Protel binary library format. Both OrCAD and Protel use the same default extensions for schematic

and library les, so if you do not wish to overwrite the original OrCAD les, save the Protel versions to a

different folder.





Figure 1.0 FT232BM – 5 volt Bus Powered Example Schematic ( 232-5VB )

D E C O U P L I N G C A P S

U S B

( O p

t i o n a

l )

F T 2 3 2 B A P P

L I C A T I O N S C H E M A T I C

I N T E R F A C I N G T O 5 V L O G I C - B U S P O W E R E D ( < = 1 0 0 m A ) A P P L I C A T I O N

5 v

M C U o r

L o g

i c c c

t

R X D

T X D

C T S #

R T S #

P O W E R D N #

V C C - 5 v

G N D

R E S E T #

R S T O U T #

S L E E P #

R S T O U T #

V C C

V C C

V C C

V C C

V C C

V C C

V C C

R 6

1 k 5

U 2

9 3 C 4 6 / 5 6 / 6 6

1 2 3 4

8 7 6 5

C S

S K

D I N

D O U T

V C C

N C

N C

G N D

R 1

1 0 k

C N 1

C N - U

S B

1 2 3 4

5

F B 1

F E R R I T E B E A D

1

2

C 5

1 0 n

F

C 4

3 3 n

F

R 5

2 7 R

R 4

2 7 R

Y 1

6 M H z

R E S O N A T O R

R 2

2 k 2

R 3

4 7 0 R

C 6

0 . 1

u F

C 2

0 . 1

u F

C 1

0 . 1

u F

C 3

1 0 u

F

U 1

F T 2 3 2 B M

2 5

2 4

2 3

2 2

2 1

2 0

1 9

5 2 8 4

3 2 1 2

2 9

9

1 8

1 7

3 1

1 4

1 5

1 6

1 2

1 0

1 1

1 3

6

3 0

2 6

3

8 7 2 7

T X D

R X D

R T S #

C T S #

D T R #

D S R #

D C D #

R S T O U T #

X T O U T

R E S E T #

E E C S

E E S K

E E D A T A

A G N D

G N D

R I #

G N D

T E S T

P W R C T L

P W R E N #

T X D E N

T X L E D #

S L E E P #

R X L E D #

V C C - I O

3 V 3 O U T

A V C C

V C C

V C C

U S B D M

U S B D P

X T I N

C 7

0 . 1

u F

R 7

4 7 k





Figure 1.0 is an example of a 5 volt, USB bus powered design using the FT232BM connected to a 5v MCU or

other external logic.

• In this example, we assume that the total current of the design is <= 100mA ( low power ), and that the

MCU / logic can detect USB suspend mode using either the SLEEP# or PWREN# pins of the FT232BM and

put itself and any circuitry it is controlling into a low power state in order to meet the total USB suspend

current requirement of 500uA or less.

• RSTOUT# is used to provide a power-on reset to the external logic in this example. If the MCU has it’s

own power-on reset logic then there is usually no need to use RSTOUT# to reset the device and this

connection and the 47k pull-down can be omitted.

• PWRCTL is tied to GND to tell the device to indicate a bus powered device in it’s USB descriptor.

• RTS / CTS handshaking is used in this example. If the MCU has no dedicated handshaking signals then

general purpose IO pins can usually be used to implement the handshaking. If the MCU is guaranteed to

accept data sent from the FT232BM at the programmed baud rate, then a single wire handshake will do (

tie CTS# of the FT232BM to GND ).

General Design Notes:

• SLEEP# goes inactive ( high ) at power-on and goes low during USB suspend. PWREN# is high on

power-on and only goes low ( active ) after the device has been congured ( successfully enumerated )

by USB. During USB suspend PWREN# will go high – the opposite polarity to SLEEP#. For a low power

bus powered USB device , either SLEEP# or PWREN# can be used for power control, however for a high

power bus powered USB device ( 100mA .. 500mA ) you must use PWREN# for power control as no USB

device is allowed to draw more than 100mA from the bus until USB conguration is complete.

• RSTOUT# has no pull-down capability – it drives to 3.3v when not in reset, and goes tri-state during

power-on reset. If used to reset an external device, a pull-down resistor must be added to make it low

during reset.

• When RTS/CTS hardware handshaking is enabled CTS# can be used to stop the FT232BM transmitting

data to the MCU / external logic. When CTS# is active ( low ) the FT232BM will transmit any data in it’s

internal buffers. On taking CTS# high, the FT232BM will stop transmitting data. Due to the asynchronous

nature of the interface, there is a latency of 0 to 3 characters between taking CTS# high and data

transmission stopping. The FT232BM drives RTS# high when the available buffer space inside the device

drops below 32 bytes. This allows the MCU / logic to continue to send up to 30 characters to the FT232BM

after RTS# goes high without causing buffer over-run.

• A suitable 3-pin ceramic resonator could be a Murata CSTCR6M00G15 or equivalent. See http://

www.murata.com/catalog/p63e.pdf for details If you prefer to use a 2 pin resonator or a crystal refer to

Figures 4 and 5 of the FT232BM data sheet for details.

• A suitable ferrite bead could be a Steward MI0805K400R-00 or equivalent. This is also available from

DigiKey as Part # 240-1035-1. For specications consult the Steward web site - http://www.steward.com

http://www.steward.com/

http://www.steward.com/





Figure 2.0 FT232BM – 5 volt Self Powered Example Schematic ( 232-5VS )


U S

B

( O p

t i o n a

l )

F T 2 3 2 B A P P L I C A T I O N S C H E M A T I C

5 v

M C U o r

L o g

i c c c

t

I N T E R F A

C I N G T O 5 V L O G I C - S E L F P O W

E R E D A P P L I C A T I O N

U P D A T E D 2 1 s t J a n u a r y 2 0 0 3

R X D

T X D

C T S #

R T S #

P O W E R D N #

V C C - 5 v

G N D

E X T E R N A L 5 V P

O W E R

S L E E P #

V C C

V C C

V C C

V C C

V C C

V C C

V C C

R 7

1 k 5

U 2

9 3 C 4 6 / 5 6 / 6 6

1 2 3 4

8 7 6 5

C S

S K

D I N

D O U T

V C C

N C

N C

G N D

R 1

1 0 k

C N 1

C N - U S B

1 2 3 4

5

C 4

3 3 n

F

R 5

2 7 R

R 4

2 7 R

Y 1

6 M H z

R E S O N

A T O R

R 2

2 k 2

R 6

1 0 k

R 3

4 7 0 R

C 5

0 . 1

u F

C 2

0 . 1

u F

C 1

0 . 1

u F

C 3

1 0 u

F

U 1

F T 2 3 2 B M

2 5

2 4

2 3

2 2

2 1

2 0

1 9

5 2 8 4

3 2 1 2

2 9

9

1 8

1 7

3 1

1 4

1 5

1 6

1 2

1 0

1 1

1 3

6

3 0

2 6

3

8 7 2 7

T

X D

R

X D

R T S #

C T S #

D T R #

D S

R #

D C

D #

R S T O U T #

X T O U T

R E S E T #

E E C S

E E S K

E E D A T A

A G N D

G N D

R I #

G N D

T E S T

P W R C T L

P W R E

N #

T X D

E N

T X L E

D #

S L E E P #

R X L E

D #

V C C - I O

3 V 3 O U T

A V C C

V C C

V C C

U S B D M

U S B D P

X T I N

C 6

0 . 1

u F

R 8

1 5 k

V C C

G N D





Figure 2.0 is an example of a 5 volt, USB self powered design using the FT232BM connected to a 5v MCU or

other external logic. A USB self power design has it’s own PSU and does not draw it’s power from the USB

bus. In such a case, no special care need be taken to meet the USB suspend current ( 0.5mA ) as the device

does not get its power from the USB port.

• In this case it is still useful to connect SLEEP# ( or PWREN# ) to the CPU as this will let the CPU know

that the PC is in suspend mode and thus unable to communicate with the device. If the device requires to

“wake up” the PC then the MCU should connect one of it’s IO Ports to the Ring Indicator pin ( RI# ). The

default state of RI# should be high - strobing this low for a few milliseconds then taking it high again will

cause a USB resume sequence thus requesting the PC to wake up. To use this feature, Remote Wake-Up

must be enabled in the 93C46 EEPROM.

• PWRCTL is tied to VCC to tell the device to indicate a self powered device in it’s USB descriptor.

•

RTS / CTS handshaking is used in this example. If the MCU has no dedicated handshaking signals thengeneral purpose IO pins can usually be used to implement the handshaking. If the MCU is guaranteed to



• Self powered designs should NOT force current back into the Host PC ( or HUB ) via the USB Port when

the said Host / Hub is powered down and the self powered device is still powered-up from it’s own

PSU. This rule includes injecting current into the powered down Host / Hub via the 1k5 pull-up on USB

D+. Failure to do this can result in unreliable operation in the eld. This is an integral part of the USB

specication and applies to all USB Self Powered devices ( not just FT232BM peripherals ). In this design,

the presence of power on the host/hub USB port is used to control the RESET# pin of the FT232BM.

When the Host / Hub is powered up RSTOUT# pulls the top end of the 1k5 resistor on USB D+ to 3.3vnominal thus identifying the device as a full speed device to USB. When the Host / HUB powers down,

the FT232BM is reset and RSTOUT# will go low thus preventing current being injected into the Host / Hub

USB D+ line via the 1k5 resistor.

General Design Notes – See Previous Example





Figure 3.0

FT232BM – 5 volt Bus Powered Example Schematic with Power Switching ( 232-5VSW )


U S B

( O p

t i o n a

l )

F T 2 3 2 B A P P


5 v

M C U o r

L o g

i c c c

t

W I T H P O W

E R S W I T C H I N G

S o

f t S t a r t

C i r c u

i t

P O W E R E D A P P L I C A T I O N

R X D

T X D

C T S #

R T S #

V C C - 5 v

G N D

V C C

V C C

V C C

V C C

V C C

V C C

R 6

1 k 5

U 2

9 3 C 4 6 / 5 6 / 6 6

1 2 3 4

8 7 6 5

C S

S K

D I N

D O U T

V

C C

N C

N C

G

N D

R 1

1 0 k

C N 1

C N - U

S B

1 2 3 4

5

F B 1


1

2

C 5

1 0 n

F

C 4

3 3 n

F

R 5

2 7 R

R 4

2 7 R

Y 1

6 M H z

R E S O N A T O R

R 2

2 k 2

R 3

4 7 0 R

C 6

0 . 1

u F

C 2

0 . 1

u F

C 1

0 . 1

u F

C 3

1 0 u

F

U 1

F T 2 3 2 B M

2 5

2 4

2 3

2 2

2 1

2 0

1 9

5 2 8 4

3 2 1 2

2 9

9

1 8

1 7

3 1

1 4

1 5

1 6

1 2

1 0

1 1

1 3

6

3 0

2 6

3

8 7 2 7

T X D

R X D

R T S #

C T S #

D T R #

D S R #

D C D #

R S T O U T #

X T O U T

R E S E T #

E E C S

E E S K

E E D A T A

A G N D

G N D

R I #

G N D

T E S T

P W R C T L

P W R E N #

T X D E N

T X L E D #

S L E E P #

R X L E D #

V C C - I O

3 V 3 O U T

A V C C

V C C

V C C

U S B D M

U S B D P

X T I N

R 7

1 k

C 8

0 . 1

u F

C 7

0 . 1

u F

Q 1

I R L M L 6 4 0 2





Figure 3.0 is an example of a 5 volt, USB bus powered design using the FT232BM connected to a 5v MCU or

other external logic. In this design, the FT232BM controls the power to the auxiliary circuitry using PWEREN#

to shut off power to this circuitry when –

1. The FT232BM is in reset, OR

2. The FT232BM has not yet been congured ( successfully recognised and enumerated over USB ), OR

3. USB is in suspend / sleep mode.

• A P-Channel Logic Level MOSFET is used as a power switch to control the power to the auxiliary devices

– in this example we use a International Rectier part number IRLML6402. R7 and C8 form a “soft start”

circuit which limits the current surge when the MOSFET turns on. Without this, there is a danger that the

transient power surge of the MOSFET turning on will reset the FT232BM or the USB Host / Hub controller.

The values used allow the attached circuitry to power up with a slew rate of ~ 12.5v per millisecond, in

other words the output voltage will transitioning from GND to 5v in around 400uS.

• When using this circuit, enable the “Pull-Down on Suspend” option in the EEPROM. This will ensure

minimum leakage current during sleep ( suspend ) mode by gently pulling down the UART interface pins

of the FT232BM pins to GND during USB suspend.

• The auxiliary circuitry attached to the FT232BM device must have it’s own power-on-reset circuitry and

should NOT use RESETO# to generate a reset for this circuitry. RESETO# does not generate a reset

during USB sleep ( suspend ) when the auxiliary logic is powered-off, thus cannot be used as a reset in

this case.

• A “USB High-Power Bus Powered Device” ( one that consumes more than 100mA and up to 500mA )

of current from the USB bus during normal operation must use this power control feature to remain

compliant as the USB specication does not allow a USB peripheral to draw more than 100mA of current

from the USB Bus until the device has been successfully enumerated. A “USB High-Power Bus Powered

Device” cannot be plugged into a USB Bus-Powered Hub as these can only supply 100mA per USB port.

• The Power ( current ) consumption of the device is set in a eld in the 93C46 EEPROM attached to the

FT232BM. A “USB High-Power Bus Powered Device” must use the 93C46 to inform the system of it’s

power requirements.






General Design Notes – See Previous Examples





Figure 4.0 FT232BM – 3.3 volt Bus Powered Example Schematic ( 232-3VB )


U S B

( O p

t i o n a

l )

F T 2 3 2 B A P

P L I C A T I O N S C H E M A T I C

I N T E R F A C I N G T O

3 . 3 V L O G I C - B U S P O W E R E D (

< = 1 0 0 m A ) A P P L I C A T I O N

3 . 3

v M C U o r

L o g

i c c c

t

R X D

T X D

C T S #

R T S #

P O W E R D N #

G N D

V C C - 3 . 3

v

R E S E T #

V C C - 3 . 3

V

R S T O U T #

S L E E P #

R S T O U T #

V C C

V C C

V C C

V C C

V C C

V C C

I

O

G

U 3

L D O R E G U L A T O R 3

. 3 v

R 6

1 k 5

U 2

9 3 C 4 6 / 5 6

/ 6 6

1 2 3 4

8 7 6 5

C S

S K

D I N

D O U T

V C C

N C

N C

G N D

R 1

1 0 k

C N 1

C N - U

S B

1 2 3 4

5

F B 1


1

2

C 5

1 0 n

F

C 4

3 3 n

F

R 5

2 7 R

R 4

2 7 R

Y 1

6 M H z

R E S O N A T O R

R 2

2 k 2

R 3

4 7 0 R

C 6

0 . 1

u F

R 7

4 7 k

C 2

0 . 1

u F

C 1

0 . 1

u F

C 3

1 0 u

F

U 1

F T 2 3 2 B M

2 5

2 4

2 3

2 2

2 1

2 0

1 9

5 2 8 4

3 2 1 2

2 9

9

1 8

1 7

3 1

1 4

1 5

1 6

1 2

1 0

1 1

1 3

6

3 0

2 6 3

8 7 2 7

T X D

R X D

R T S #

C T S #

D T R #

D S R #

D C D #

R S T O U T #

X T O U T

R E S E T #

E E C S

E E S K

E E D A T A

A G N D

G N D

R I #

G N D

T E S T

P W R C T L

P W R E N #

T X D E N

T X L E D #

S L E E P #

R X L E D #

V C C - I O

3 V 3 O U T

A V C C

V C C

V C C

U S B D M

U S B D P

X T I N

C 7

0 . 1

u F





Figure 4.0 is an example of a 3.3 volt, USB bus powered design using the FT232BM connected to a 3.3v MCU

or other external logic.

• The main difference between this circuit and the 5 volt circuit of Figure 1.0 is that a 3.3 volt LDO regulator

i.c. is used to provide a 3.3v supply to the auxiliary circuiry.

• VCC-IO is driven from the 3.3v LDO regulator i.c. in order to drive the UART interface from the FT232BM to

the MCU / external logic at 3.3v level instead of 5v level.

• As the USB supply rail can drop to 4.4 volts or less under load, an LDO ( Low Dropout ) voltage regulator

must be used in this instance.

• The 3.3v LDO voltage regulator must also have a low quiescent ( no load ) current in order to ensure that

the USB suspend current requirement ( <= 500uA ) is met during USB suspend.

• In this example, we assume that the total current of the design is <= 100mA ( low power ), and that the

MCU / logic can detect USB suspend mode using either the SLEEP# or PWREN# pins of the FT232BM and

put itself and any circuitry it is controlling into a low power state in order to meet the total USB suspend

current requirement of 500uA or less.

• RSTOUT# is used to provide a power-on reset to the external logic in this example. If the MCU has it’s

own power-on reset logic then there is usually no need to use RSTOUT# to reset the device and this

connection and the 47k pull-down can be omitted. Note : If RSTOUT# is used to reset an external device

AND to pull-up the USB D+ line, it’s Vout high can be as low as 2.2v so it must be used to drive a TTL level

reset input on the external device.











Figure 5.0 FT232BM – 3.3 volt Self Powered Example Schematic ( 232-3VS )


U S B

( O p

t i o n a

l )

F T 2 3 2 B A P P


3 . 3

v M C U o r

L o g

i c c c

t

I N T E R F A C I N G T O 3 . 3

V L O G I C - S E L F

P O W E R E D A P P L I C A T I O N

U P D A T E D 2 1 s t J a n u a r y 2 0 0 3

R X D

T X D

C T S #

R T S #

V C C - 3 v

G N D

E X T E R N A L P O W

E R

P O W E R E N #

V C C

V C C

V C C

V C C

V C C

V C C 3 V V

C C 3 V

R 6

1 k 5

U 2

9 3 C 4 6 / 5 6 / 6 6

1 2 3 4

8 7 6 5

C S

S K

D I N

D O U T

V

C C

N C

N C

G

N D

R 1

1 0 k

C N 1

C N - U

S B

1 2 3 4

5

C 4

3 3 n

F

R 5

2 7 R

R 4

2 7 R

Y 1

6 M H z

R E S O N A T O R

R 2

2 k 2

R 8

1 0 k

R 7

1 5 k

R 3

4 7 0 R

C 5

0 . 1

u F

C 2

0 . 1

u F

C 1

0 . 1

u F

C 3

1 0 u

F

U 1

F T 2 3 2 B M

2 5

2 4

2 3

2 2

2 1

2 0

1 9

5 2 8 4

3 2 1 2

2 9

9

1 8

1 7

3 1

1 4

1 5

1 6

1 2

1 0

1 1

1 3

6

3 0

2 6

3

8 7 2 7

T X D

R X D

R T S #

C T S #

D T R #

D S R #

D C D #

R S T O U T #

X T O U T

R E S E T #

E E C S

E E S K

E E D A T A

A G N D

G N D

R I #

G N D

T E S T

P W R C T L

P W R E N #

T X D E N

T X L E D #

S L E E P #

R X L E D #

V C C - I O

3 V 3 O U T

A V C C

V C C

V C C

U S B D M

U S B D P

X T I N

C 6

0 . 1

u F

G N D

V C C 3 . 3 v

V C C 5 . 0 v





Figure 5.0 is an example of a 3.3 volt, USB self powered design using the FT232BM connected to a 3.3v MCU

or other external logic. A USB self power design has it’s own PSU and does not draw it’s power from the USB

bus. In such a case, no special care need be taken to meet the USB suspend current ( 0.5mA ) as the devicedoes not get its power from the USB port. The differences between this circuit and that of Figure 2.0 are

minimal. See the notes in Figure 2 for the main details.

• In this case the internal PSU needs to supply 3.3 volts to the auxiliary circuitry and 5 volts to the

FT232BM i.c.

• The VCCIO power line to the FT232BM is driven from the 3.3v supply in order to drive the auxiliary logic at

the correct voltage level.

Important Note : In this design, the PWRCTL Pin ( Pin 14 ) of the FT232BM is tied high to indicate a self

powered design. It is important to tie this to VCCIO ( 3.3v ) and NOT to VCC ( 5.0v ) otherwise the input

protection diodes on this pin will conduct and try to pull VCCIO towards 5.0v

As well as being undesirable, this may cause excessive current to be drawn by the FT232BM and the 3.3v

logic attached to this device.





Figure 6.0 FT232BM – 3.3 volt Switched Power Bus Powered Schematic ( 232-3VSW)


U S

B

( O p

t i o n a

l )

F T 2 3 2 B A P P L I C

A T I O N S C H E M A T I C

3 v

M C U o r

L o g

i c c c

t

W I T H P O W E R S W I T C H I N G

I N T E R F A C I N G T O 3 . 3

V L O G I C - B U S P

O W E R E D ( < = 2 5 0 m A ) A P P L I C A

T I O N

S o

f t S t a r t

C i r c u

i t

R X D

T X D

C T S #

R T S #

V C C - 3 v

G N D

V C C

V C C

V C C

V C C

V C C

V C C

R 6

1 k 5

U 2

9 3 C 4 6 / 5 6 / 6 6

1 2 3 4

8 7 6 5

C S

S K

D I N

D O U T

V C C

N C

N C

G N D

R 1

1 0 k

C N

1

C N

- U S B

1 2 3 4

5

F B 1


1

2

C 4

1 0 n

F

C 3

3 3 n

F

R 5

2 7 R

R 4

2 7 R

Y 1

6 M H z

R E S O N A T O R

R 2

2 k 2

C 1 0

0 . 1

u F

R 7

1 k

Q 1

I R L M L 6 4 0 2

C 9

0 . 1

u F

G

V i

V o

R E G 1

T C 5 5 R P 3 3 0 2

1

2

3

R 3

4 7 0 R

C 5

0 . 1

u F

C 2

0 . 1

u F

C 1

0 . 1

u F

C 7

4 . 7

u F

C 8

4 . 7

u F

U 1

F T 2 3 2 B M

2 5

2 4

2 3

2 2

2 1

2 0

1 9

5 2 8 4

3 2 1 2

2 9

9

1 8

1 7

3 1

1 4

1 5

1 6

1 2

1 0

1 1

1 3

6

3 0

2 6

3

8 7 2 7

T X D

R X D

R T S #

C T S #

D T R #

D

S R #

D

C D #

R S T O U T #

X T O U T

R E S E T #

E E C S

E E S K

E E D A T A

A G N D

G N D

R I #

G N D

T E S T

P W R C T L

P W R

E N #

T X

D E N

T X L E D #

S L E E P #

R X L E D #

V C C - I O

3 V 3 O U T

A V C C

V C C

V C C

U S B D M

U S B D P

X T I N

C 6

0 . 1

u F





Figure 6.0 is an example of a 3.3 volt, USB bus powered design with power switching using the FT232BM

connected to a 3.3v MCU or other external logic. The circuit is essentially a combination of the schematics of

Figure 3 and Figure 4.

• A 3.3 volt LDO regulator i.c. is used to provide a 3.3v VCCIO rail and switched 3.3v supply to the auxiliary

circuiry via a IRLML6402 P-Channel MOSFET .

• In this example, we use a Telcom / MicroChip TC55RP3302 as the 3.3v LDO regulator. This has a maximum

rated output current of 250mA. If a higher current is required, use an LD1117 / LM1117 series LDO

regulator instead as these are rated to 800mA. The two are not pin compatible.

• R7 and C10 form a soft start circuit which helps prevent excesssive power switching transients when the

MOSFET turns on. We would advise you to include these components as without them the current surge

when the IRLML6402 MOSFET initially turns on can be capable of resetting the FT232BM or tripping the

power sense circuitry in a USB hub.






Figure 7.0 FT232BM –5v BUS Powered USB => RS232 Converter Example Schematic ( USB-232B )


M A X 2 1 3 C W I

A D M 2 1 3 E

S P 2 1 3 E C A

T X

R X

U

S B

( O p t i o n a l )

U S B < = > R S 2 3 2 S E R I A L C O N V E R T E R (

3 0 0 t o 1 1 5 k / 4 6 0 k b a u d )

S P 2 1 3 E H C A

F T 2 3 2 B A P P L I C A T I O N

S C H E M A T I C

R I

D T R

C T S

T X D A T A

S H I E L D

R T S

T X D

R X D A T A

D S R

R X D

D C D

R T S #

C T S #

D T R #

S H I E L D

D S R #

D C D #

R I #

T X D

T X D A T A

D T R #

D T R

R T S #

R T S

C T S

C T S #

D S R

D S R #

D C D

D C D #

R X D A T A

R X D

S L E E P #

R I

R I #

S L E E P

#

V C C

V C C

G N D

V C C

V C C

V C C

V C C

V C C

V C C

V C

C

V C C

V C C

V C C

C 1

0 . 1 u F

C 2

0 . 1 u F

C 3

0 . 1 u F

C 4

1 0 u F

D 1

L E D

R 1

2 2 0 R

C 5

0 . 1 u F

C 6

0 . 1 u F

U 1

M A X 2 1 3 C A I

7 6 2 0

2 1 9 4

2 7

2 3

1 8

2 3 1 2 8

8 5 2 6

2 2

1 9

2 5

2 4

1 3

1 7

1 2

1 4

1 5

1 6

1 0

1 1

T 1 I N

T 2 I N

T 3 I N

T 4 I N

R 1 I N

R 2 I N

R 3 I N

R 4 I N

R 5 I N

T 1 O U T

T 2 O U T

T 3 O U T

T 4 O U T

R 1 O U T

R 2 O U T

R 3 O U T

R 4 O U T

R 5 O U T

S H D N #

E N

V +

V -

C 1 +

C 1 -

C 2 +

C 2 -

G N D

V C C

C 7

0 . 1 u F

C 8

0 . 1 u F

S K T 1

D B 9 M

5 94 8 3 7 2 6 1

1 0

D 2

L E D

R 2

2 2 0 R

C

N 1

C

N - U S B

1 2 3 4

5

R 3

1 0 k

C 9

3 3 n F

C 1 0

1 0 n F

R 4

2 k 2

F B 1


1

2

C 1 1

0 . 1 u F

R 5

4 7 0 R

U 2

F T 2 3 2 B M

2 5

2 4

2 3

2 2

2 1

2 0

1 9

5 2 8 4

3 2 1 2

2 9

9

1 8

1 7

3 1

1 4

1 5

1 6

1 2

1 0

1 1

1 3

6

3 0

2 6

3

8 7 2 7

T X D

R X D

R T S #

C T S #

D T R #

D S R #

D C D #

R S T O U T #

X T O U T

R E S E T #

E E C S

E E S K

E E D A T A

A G N D

G N D

R I #

G N D

T E S T

P W R C T L

P W R E N #

T X D E N

T X L E D #

S L E E P #

R X L E D #

V C C - I O

3 V 3 O U T

A V C C

V C C

V C C

U S B D M

U S B D P

X T I N

Y 1

6 M H z R E S O N A T O R

R 6

2 7 R

R 7

2 7 R

R 8

1 k 5

U 3

9 3 C 4 6 / 5 6 / 6 6

1 2 3 4

8 7 6 5

C S

S K

D I N

D O U T

V C C

N C

N C

G N D





Figure 7.0 is an example of a 5 volt, USB bus powered design using the FT232BM connected to a TTL ó

RS232 level converter i.c .

•

For RS232 applications, the baud rate of the nished product is limited by the ac. driving characteristicsof the level converter i.c. rather than that of the FT232BM.

• This example uses the popular “213” series of TTL to RS232 level converters. These devices have 4

transmitters and 5 receivers in a 28 LD SSOP package and feature an in-built voltage converter to convert

the 5v ( nominal ) VCC to the +/- 9volts required by RS232. An important feature of these devices is the

SHDN# pin which can power down the device to a low quiescent current during USB suspend mode

• The device used in this schematic is a Sipex SP213EHCA which is capable of RS232 communication

at up to 500k baud. If a lower baud rate is acceptable, then several pin compatible alternatives are

available such as Sipex SP213ECA , Maxim MAX213CAI and Analog Devices ADM213E which are good

for communication at up to 115,200 baud. If a higher baud rate is desired, use a Maxim MAX3245CAI part

which is capable of RS232 communication at rates of up to 1M baud.• Note : the MAX3245 is not pin compatible with the 213 series devices, also it’s SHDN pin is active high so

connect this to PWREN# instead of SLEEP#.





Document Revision History

DG232B Version 1.0 – Initial document created 05 August 2002

DG232B Version 1.1 - Created 06 August 2002

• Added USB-232B application

DG232B Version 2.0 - Created 19th May 2003

• Corrected Pull Up Control Circuit for Self Powered Designs

• Corrected connection of PWRCTL in 3.3v Self Powered Designs

• Updated Schematic Drawings

• Added 3.3v Switched Bus Powered reference schematic

Disclaimer

© Future Technology Devices International Limited , 2002 / 2003

Neither the whole nor any part of the information contained in, or the product described in this manual, may

be adapted or reproduced in any material or electronic form without the prior written consent of the copyright

holder.

This product and its documentation are supplied on an as-is basis and no warranty as to their suitability for

any particular purpose is either made or implied.

Future Technology Devices International Ltd. will not accept any claim for damages howsoever arising as a

result of use or failure of this product. Your statutory rights are not affected.This product or any variant of it is not intended for use in any medical appliance, device or system in which

the failure of the product might reasonably be expected to result in personal injury.

The information in this document may be subject to change without notice.

Contact Information

Future Technology Devices Intl. Limited

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Glasgow G3 6JA,

United Kingdom.

Tel : +44 ( 0 )141 353 2565

Fax : +44 ( 0 )141 353 2656

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