MAXIM MAX3222, MAX3232, MAX3237, MAX3241 User Manual

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_______________General Description

The MAX3222/MAX3232/MAX3237/MAX3241 trans­ceivers have a proprietary low-dropout transmitter out­put stage enabling true RS-232 performance from a

3.0V to 5.5V supply with a dual charge pump. The
devices require only four small 0.1µF external charge­pump capacitors. The MAX3222, MAX3232, and
MAX3241 are guaranteed to run at data rates of
120kbps while maintaining RS-232 output levels. The
MAX3237 is guaranteed to run at data rates of 250kbps
in the normal operating mode and 1Mbps in the
MegaBaud™ operating mode, while maintaining RS-232
output levels.

The MAX3222/MAX3232 have 2 receivers and 2
drivers. The MAX3222 features a 1µA shutdown mode
that reduces power consumption and extends battery
life in portable systems. Its receivers remain active in
shutdown mode, allowing external devices such as
modems to be monitored using only 1µA supply cur­rent. The MAX3222 and MAX3232 are pin, package,
and functionally compatible with the industry-standard
MAX242 and MAX232, respectively.

The MAX3241 is a complete serial port (3 drivers/
5 receivers) designed for notebook and subnotebook
computers. The MAX3237 (5 drivers/3 receivers) is ideal
for fast modem applications. Both these devices feature
a shutdown mode in which all receivers can remain
active while using only 1µA supply current. Receivers R1
(MAX3237/MAX3241) and R2 (MAX3241) have extra out­puts in addition to their standard outputs. These extra
outputs are always active, allowing external devices
such as a modem to be monitored without forward bias­ing the protection diodes in circuitry that may have V

CC

completely removed.
The MAX3222, MAX3237, and MAX3241 are available

in space-saving TSSOP and SSOP packages.

________________________Applications

Notebook, Subnotebook, and Palmtop Computers
High-Speed Modems
Battery-Powered Equipment
Hand-Held Equipment
Peripherals
Printers

____________________________Features

♦ Low Supply Current:

300µA (MAX3222/MAX3232/MAX3241)
500µA (MAX3237)

♦ Guaranteed Data Rate:

120kbps (MAX3222/MAX3232/MAX3241)
250kbps (MAX3237—Normal Operation)
1Mbps (MAX3237—MegaBaud Operation)

♦ 1µA Low-Power Shutdown with Receivers Active

(MAX3222/MAX3237/MAX3241)

♦ Flow-Through Pinout (MAX3237)
♦ Meets EIA/TIA-232 Specifications Down to 3.0V
♦ Guaranteed Mouse Driveability (MAX3241)
♦ Pin Compatible with Industry-Standard MAX232

(MAX3232)
Pin Compatible with Industry-Standard MAX242
(MAX3222)

♦ Guaranteed Slew Rate:

6V/µs (MAX3222/MAX3232/MAX3237/MAX3241)
24V/µs (MAX3237—MegaBaud Operation)

MAX3222/MAX3232/MAX3237/MAX3241*

3.0V to 5.5V, Low-Power, up to 1Mbps, True RS-232

Transceivers Using Four 0.1µF External Capacitors

________________________________________________________________

Maxim Integrated Products

1

18
17
16
15
14
13
12
11

1
2
3
4
5
6
7
8

SHDN
V

CC

GND
T1OUT

C1-

V+

C1+

EN

TOP VIEW

R1IN
R1OUT
T1IN
T2IN

T2OUT

V-

C2-

C2+

10

9

R2OUTR2IN

DIP/SO

MAX3222

_________________Pin Configurations

______________Ordering Information

19-0273; Rev 5; 3/99

PART TEMP. RANGE PIN-PACKAGE

MegaBaud is a trademark of Maxim Integrated Products.
*Covered by U.S. Patent numbers 4,636,930; 4,679,134; 4,777,577; 4,797,899; 4,809,152; 4,897,774; 4,999,761; and other patents pending.

Typical Operating Circuits appear at end of data sheet.

Pin Configurations continued at end of data sheet.

Ordering Information continued at end of data sheet.

MAX3222CUP

0°C to +70°C 20 TSSOP
MAX3222CAP 0°C to +70°C 20 SSOP
MAX3222CWN 0°C to +70°C 18 SO
MAX3222CPN 0°C to +70°C 18 Plastic DIP

VCC= 5.0V

MAX3222/MAX3232/MAX3237/MAX3241

3.0V to 5.5V, Low-Power, up to 1Mbps, True RS-232
Transceivers Using Four 0.1µF External Capacitors

2 _______________________________________________________________________________________

ABSOLUTE MAXIMUM RATINGS

ELECTRICAL CHARACTERISTICS

(VCC= +3.0V to +5.5V, C1–C4 = 0.1µF (Note 2), TA= T

MIN

to T

MAX

, unless otherwise noted. Typical values are at TA= +25°C.)

Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.

Note 1: V+ and V- can have a maximum magnitude of 7V, but their absolute difference cannot exceed 13V.

V

CC

...........................................................................-0.3V to +6V

V+ (Note 1)...............................................................-0.3V to +7V

V- (Note 1)................................................................+0.3V to -7V

V+ + V- (Note 1)...................................................................+13V

Input Voltages

T_IN,

SHDN, EN ...................................................-0.3V to +6V

MBAUD...................................................-0.3V to (V

CC

+ 0.3V)

R_IN.................................................................................±25V

Output Voltages

T_OUT...........................................................................±13.2V

R_OUT....................................................-0.3V to (V

CC

+ 0.3V)

Short-Circuit Duration

T_OUT....................................................................Continuous

Continuous Power Dissipation (T

A

= +70°C)
16-Pin Plastic DIP (derate 10.53mW/°C above +70°C)...842mW

16-Pin Narrow SO (derate 8.70mW/°C above +70°C) ....696mW

16-Pin Wide SO (derate 9.52mW/°C above +70°C)........762mW

16-Pin TSSOP (derate 6.7mW/°C above +70°C).............533mW

18-Pin Plastic DIP (derate 11.11mW/°C above +70°C) ..889mW

18-Pin SO (derate 9.52mW/°C above +70°C)..............762mW

20-Pin SSOP (derate 8.00mW/°C above +70°C) .........640mW

20-Pin TSSOP (derate 7.0mW/°C above +70°C).............559mW

28-Pin SO (derate 12.50mW/°C above +70°C).....................1W

28-Pin SSOP (derate 9.52mW/°C above +70°C) .........762mW

28-Pin TSSOP (derate 8.7mW/°C above +70°C).............696mW

Operating Temperature Ranges

MAX32_ _C_ _.....................................................0°C to +70°C

MAX32_ _E_ _ .................................................-40°C to +85°C

Storage Temperature Range.............................-65°C to +150°C

Lead Temperature (soldering, 10sec).............................+300°C

I

OUT

= -1.0mA

I

OUT

= 1.6mA

Receivers disabled

T_IN, EN, SHDN, MBAUD

T_IN, EN, SHDN, MBAUD

CONDITIONS

V

0.8 1.5

Input Threshold Low

0.6 1.2

V-25 25Input Voltage Range

0.5 2.0

VCCPower-Supply Current

VVCC- 0.6 VCC- 0.1Output Voltage High

V0.4Output Voltage Low

µA±0.05 ±10Output Leakage Current

µA±0.01 ±1.0Input Leakage Current

V0.8

Input Logic Threshold Low
(Note 3)

UNITS

MIN TYP MAX

PARAMETER

TA= +25°C

TA= +25°C

V

1.8 2.4

Input Threshold High

1.5 2.4

VCC= 3.3V
VCC= 5.0V

2.0
V

2.4

Input Logic Threshold High
(Note 3)

No load, VCC= 3.3V or 5.0V,
TA= +25°C

mA

0.3 1.0

MAX3222/MAX3232/
MAX3241

MAX3237

SHDN = GND, TA= +25°C µA1.0 10Shutdown Supply Current

VCC= 3.3V
VCC= 5.0V
VCC= 3.3V
VCC= 5.0V

DC CHARACTERISTICS

LOGIC INPUTS AND RECEIVER OUTPUTS

RECEIVER INPUTS

MAX3222/MAX3232/MAX3237/MAX3241

3.0V to 5.5V, Low-Power, up to 1Mbps, True RS-232

Transceivers Using Four 0.1µF External Capacitors

_______________________________________________________________________________________ 3

TIMING CHARACTERISTICS—MAX3222/MAX3232/MAX3241

(VCC= +3.0V to +5.5V, C1–C4 = 0.1µF (Note 2), TA= T

MIN

to T

MAX

, unless otherwise noted. Typical values are at TA= +25°C.)

ELECTRICAL CHARACTERISTICS (continued)

(VCC= +3.0V to +5.5V, C1–C4 = 0.1µF (Note 2), TA= T

MIN

to T

MAX

, unless otherwise noted. Typical values are at TA= +25°C.)

T1IN = T2IN = GND, T3IN = VCC,
T3OUT loaded with 3kΩ to GND,
T1OUT and T2OUT loaded with 2.5mA each

CONDITIONS

V±5.0Transmitter Output Voltage

V0.3Input Hysteresis

UNITS

MIN TYP MAX

PARAMETER

All transmitter outputs loaded with 3kΩ to ground V±5.0 ±5.4Output Voltage Swing

mA±35 ±60Output Short-Circuit Current

VCC= V+ = V- = 0V, T

OUT

= ±2V Ω300 10MOutput Resistance

V

OUT

= ±12V, VCC= 0V or 3V to 5.5V, transmitters

disabled

µA±25Output Leakage Current

t

PHL

RL= 3kΩ, CL= 1000pF, one transmitter switching

t

PLH

| t

PHL

- t

PLH

|

| t

PHL

- t

PLH

|

Normal operation

Normal operation

CONDITIONS

0.3
µs

0.3

Receiver Propagation Delay

kbps120 235Maximum Data Rate

ns300Receiver Skew

ns300Transmitter Skew

ns200Receiver Output Disable Time

ns200Receiver Output Enable Time

UNITS

MIN TYP MAX

PARAMETER

630

VCC= 3.3V, RL= 3Ω to 7kΩ,
+3V to -3V or -3V to +3V,
TA= +25°C

V/µs

430

Transition-Region Slew Rate

R_IN to R_OUT, CL= 150pF

CL= 150pF to
1000pF

CL= 150pF to
2500pF

TA= +25°C kΩ357Input Resistance

MOUSE DRIVEABILITY (MAX3241)

TRANSMITTER OUTPUTS

MAX3222/MAX3232/MAX3237/MAX3241

3.0V to 5.5V, Low-Power, up to 1Mbps, True RS-232
Transceivers Using Four 0.1µF External Capacitors

4 _______________________________________________________________________________________

__________________________________________Typical Operating Characteristics

(VCC= +3.3V, 235kbps data rate, 0.1µF capacitors, all transmitters loaded with 3kΩ, TA= +25°C, unless otherwise noted.)

-6

-5

-4

-3

-2

-1

0

1

2

3

4

5

6

0

MAX3222/MAX3232

TRANSMITTER OUTPUT VOLTAGE

vs. LOAD CAPACITANCE

MAX3222-01

LOAD CAPACITANCE (pF)

TRANSMITTER OUTPUT VOLTAGE (V)

2000 30001000 4000 5000

V

OUT

+

V

OUT

-

0

2

4

6

8

10

12

14

16

18

20

22

150

MAX3222/MAX3232

SLEW RATE

vs. LOAD CAPACITANCE

MAX3222-02

LOAD CAPACITANCE (pF)

SLEW RATE (V/µs)

2000 30001000 4000 5000

FOR DATA RATES UP TO 235kbps

+SLEW

-SLEW

0

5

10

15

20

25

30

35

40

0

MAX3222/MAX3232

SUPPLY CURRENT vs. LOAD CAPACITANCE

WHEN TRANSMITTING DATA

MAX3222-03

LOAD CAPACITANCE (pF)

SUPPLY CURRENT (mA)

2000 30001000 4000 5000

235kbps

120kbps

20kbps

RL= 3kΩ, CL= 1000pF, one transmitter switching,
MBAUD = GND

Normal operation

CONDITIONS

Normal operation ns200Receiver Output Disable Time

| t

PHL

- t

PLH

|, MBAUD = GND

ns100

0.15

250

µs

0.15

Receiver Propagation Delay

ns200Receiver Output Enable Time

UNITS

MIN TYP MAX

PARAMETER

TIMING CHARACTERISTICS—MAX3237

(VCC= +3.0V to +5.5V, C1–C4 = 0.1µF (Note 2), TA= T

MIN

to T

MAX

, unless otherwise noted. Typical values are at TA= +25°C.)

VCC= 3.0V to 4.5V, RL= 3kΩ, CL= 250pF,
one transmitter switching, MBAUD = V

CC

1000

VCC= 4.5V to 5.5V, RL= 3kΩ, CL= 1000pF,
one transmitter switching, MBAUD = V

CC

kbps

1000

Maximum Data Rate

R_IN to R_OUT, CL= 150pF

| t

PHL

- t

PLH

|, MBAUD = V

CC

ns25

Transmitter Skew

| t

PHL

- t

PLH

|

ns50Receiver Skew

630

V/µs

430

t

PHL

t

PLH

CL= 150pF to 2500pF,
MBAUD = GND

CL= 150pF
to 1000pF

MBAUD =

GND
VCC= 3.3V, RL= 3Ω to 7kΩ,
+3V to -3V or -3V to +3V,
TA= +25°C

Transition-Region Slew Rate

MBAUD =

V

CC

24 150

Note 2: MAX3222/MAX3232/MAX3241: C1–C4 = 0.1µF tested at 3.3V ±10%; C1 = 0.047µF, C2–C4 = 0.33µF tested at 5.0V ±10%.

MAX3237: C1–C4 = 0.1µF tested at 3.3V ±5%; C1–C4 = 0.22µF tested at 3.3V ±10%; C1 = 0.047µF, C2–C4 = 0.33µF tested
at 5.0V ±10%.

Note 3: Transmitter input hysteresis is typically 250mV.

MAX3222/MAX3232/MAX3237/MAX3241

3.0V to 5.5V, Low-Power, up to 1Mbps, True RS-232

Transceivers Using Four 0.1µF External Capacitors

_______________________________________________________________________________________

5

-7.5

-5.0

-2.5

0

2.5

5.0

7.5

0

MAX3241

TRANSMITTER OUTPUT VOLTAGE

vs. LOAD CAPACITANCE

MAX3222-04

LOAD CAPACITANCE (pF)

TRANSMITTER OUTPUT VOLTAGE (V)

2000 30001000 4000 5000

V

OUT

+

1 TRANSMITTER AT 235kbps
2 TRANSMITTERS AT 30kbps

V

OUT

-

ALL OUTPUTS LOADED WITH 3kΩ +CL

0.1µF CHARGE-PUMP CAPACITORS
FOR ALL DATA RATES UP TO 235kbps

4

6

8

10

12

14

16

18

20

22

24

0

MAX3241

SLEW RATE

vs. LOAD CAPACITANCE

MAX3222-05

LOAD CAPACITANCE (pF)

SLEW RATE (V/µs)

2000 30001000 4000 5000

+SLEW

-SLEW

0

5

10

15

20

25

30

35

45
40

0

MAX3241

SUPPLY CURRENT vs. LOAD

CAPACITANCE WHEN TRANSMITTING DATA

MAX3222-06

LOAD CAPACITANCE (pF)

SUPPLY CURRENT (mA)

2000 30001000 4000 5000

235kbps

120kbps

20kbps

-7.5

-5.0

-2.5

0

2.5

5.0

7.5

0

MAX3237

TRANSMITTER OUTPUT VOLTAGE

vs. LOAD CAPACITANCE (MBAUD = GND)

MAX3222-07

LOAD CAPACITANCE (pF)

TRANSMITTER OUTPUT VOLTAGE (V)

2000 30001000 4000 5000

1 TRANSMITTER AT 240kbps
4 TRANSMITTERS AT 15kbps
3kΩ + C

L

LOADS

V

CC

= 3.3V

0

10

20

30

50

40

60

70

0

MAX3237

SLEW RATE vs. LOAD CAPACITANCE

(MBAUD = V

CC

)

MAX3222-10

LOAD CAPACITANCE (pF)

SLEW RATE (V/µs)

500 1000 1500 2000

-SLEW, 1Mbps
+SLEW, 1Mbps

1 TRANSMITTER AT FULL DATA RATE
4 TRANSMITTERS AT 1/16 DATA RATE
3kΩ + C

L

LOAD EACH OUTPUT

V

CC

= 3.3V

-SLEW, 2Mbps
+SLEW, 2Mbps

-7.5

-5.0

-2.5

0

2.5

5.0

7.5

0

MAX3237

TRANSMITTER OUTPUT VOLTAGE

vs. LOAD CAPACITANCE (MBAUD = V

CC

)

MAX3222-08

LOAD CAPACITANCE (pF)

TRANSMITTER OUTPUT VOLTAGE (V)

500 1000 1500 2000

1 TRANSMITTER AT FULL DATA RATE
4 TRANSMITTERS AT 1/16 DATA RATE
3kΩ + C

L

LOAD, EACH OUTPUT

V

CC

= 3.3V

2Mbps

1.5Mbps

1Mbps

2Mbps

1Mbps

1.5Mbps

0

10

20

30

40

50

60

0

MAX3237

SUPPLY CURRENT vs.

LOAD CAPACITANCE (MBAUD = GND)

MAX3222-11

LOAD CAPACITANCE (pF)

SUPPLY CURRENT (mA)

2000 30001000 4000 5000

240kbps

120kbps

20kbps

1 TRANSMITTER AT FULL DATA RATE
4 TRANSMITTERS AT 1/16 DATA RATE
3kΩ + C

L

LOADS

V

CC

= 3.3V

0

2

4

6

8

10

12

0

MAX3237

SLEW RATE vs. LOAD CAPACITANCE

(MBAUD = GND)

MAX3222-09

LOAD CAPACITANCE (pF)

SLEW RATE (V/µs)

2000 30001000 4000 5000

+SLEW

-SLEW

1 TRANSMITTER AT 240kbps
4 TRANSMITTERS AT 15kbps
3kΩ + C

L

LOADS

V

CC

= 3.3V

0

10

30

20

40

50

60

70

0

MAX3237

SKEW vs. LOAD CAPACITANCE

(t

PLH

- t

PHL

)

MAX3222-12

LOAD CAPACITANCE (pF)

1000 1500500 2000 2500

MAX

MIN

AVERAGE; 10 PARTS

SKEW (ns)

1 TRANSMITTER AT 512kbps
4 TRANSMITTERS AT 32kbps
3kΩ + C

L

LOADS

V

CC

= 3.3V

MBAUD = V

CC

_____________________________Typical Operating Characteristics (continued)

(VCC= +3.3V, 235kbps data rate, 0.1µF capacitors, all transmitters loaded with 3kΩ, TA= +25°C, unless otherwise noted.)

MAX3222/MAX3232/MAX3237/MAX3241

3.0V to 5.5V, Low-Power, up to 1Mbps, True RS-232
Transceivers Using Four 0.1µF External Capacitors

6 _______________________________________________________________________________________

—

FUNCTION

—

MAX3222

Noninverting Complementary Receiver Outputs.
Always active.

DIP/SO SSOP

— 11, 14

1 1 Receiver Enable. Active low.

2 2

Positive Terminal of Voltage-Doubler Charge-Pump
Capacitor

6 6

Negative Terminal of Inverting Charge-Pump
Capacitor

5 5

Positive Terminal of Inverting Charge-Pump
Capacitor

4 4

Negative Terminal of Voltage-Doubler Charge-Pump
Capacitor

3 3 +5.5V Generated by the Charge Pump

11, 12 12, 13 TTL/CMOS Transmitter Inputs

10, 13 10, 15 TTL/CMOS Receiver Outputs

9, 14 9, 16 RS-232 Receiver Inputs

8, 15 8, 17 RS-232 Transmitter Outputs

7 7 -5.5V Generated by the Charge Pump

18 20 Shutdown Control. Active low.

17 19 +3.0V to +5.5V Supply Voltage

16 18 Ground

No Connection

MAX3237MAX3232

— 16

— 13

1 28

5 3

4 1

3 25

2 27

10, 11

17, 19, 22,

23, 24

9, 12 18, 20, 21

8, 13 8, 9, 11

7, 14

5, 6, 7,

10, 12

6 4

— 14

16 26

15 2

— —

NAME

EN

C1+

C2-

C2+

C1-

V+

T_IN

R_OUT

R_IN

T_OUT

V-

SHDN

V

CC

GND

R_OUTB

N.C.

MAX3241

20, 21

23

28

2

1

24

27

12, 13, 14

15–19

4–8

9, 10, 11

3

22

26

25

—

PIN

— —

MegaBaud Control Input. Connect to GND for normal
operation; connect to VCCfor 1Mbps transmission rates.

— 15 MBAUD—

______________________________________________________________Pin Description

MAX3222/MAX3232/MAX3237/MAX3241

3.0V to 5.5V, Low-Power, up to 1Mbps, True RS-232

Transceivers Using Four 0.1µF External Capacitors

_______________________________________________________________________________________ 7

_______________Detailed Description

Dual Charge-Pump Voltage Converter

The MAX3222/MAX3232/MAX3237/MAX3241’s internal
power supply consists of a regulated dual charge pump
that provides output voltages of +5.5V (doubling charge
pump) and -5.5V (inverting charge pump), regardless of
the input voltage (VCC) over the 3.0V to 5.5V range. The
charge pumps operate in a discontinuous mode; if the
output voltages are less than 5.5V, the charge pumps
are enabled, and if the output voltages exceed 5.5V, the
charge pumps are disabled. Each charge pump
requires a flying capacitor (C1, C2) and a reservoir
capacitor (C3, C4) to generate the V+ and V- supplies.

RS-232 Transmitters

The transmitters are inverting level translators that con­vert CMOS-logic levels to 5.0V EIA/TIA-232 levels.

The MAX3222/MAX3232/MAX3241 transmitters guaran­tee a 120kbps data rate with worst-case loads of 3kΩ in
parallel with 1000pF, providing compatibility with PC-to­PC communication software (such as LapLink™).
Typically, these three devices can operate at data rates
of 235kbps. Transmitters can be paralleled to drive multi­ple receivers or mice.

The MAX3222/MAX3237/MAX3241’s output stage is
turned off (high impedance) when the device is in shut­down mode. When the power is off, the MAX3222/
MAX3232/MAX3237/MAX3241 permit the outputs to be
driven up to ±12V.

The transmitter inputs do not have pull-up resistors.
Connect unused inputs to GND or V

CC

.

MAX3237 MegaBaud Operation

In normal operating mode (MBAUD = GND), the
MAX3237 transmitters guarantee a 250kbps data rate
with worst-case loads of 3kΩ in parallel with 1000pF.
This provides compatibility with PC-to-PC communica­tion software, such as Laplink™.

For higher speed serial communications, the MAX3237
features MegaBaud operation. In MegaBaud operating
mode (MBAUD = VCC), the MAX3237 transmitters guar­antee a 1Mbps data rate with worst-case loads of 3kΩ in
parallel with 250pF for 3.0V < V

CC

< 4.5V. For 5V ±10%
operation, the MAX3237 transmitters guarantee a 1Mbps
data rate into worst-case loads of 3kΩ in parallel with
1000pF.

MAX3222
MAX3232
MAX3237
MAX3241

5k

R_ IN

R_ OUT

EN

*

C2-

C2+

C1-

C1+

V-

V+

V

CC

C4

C3

C1

C2

0.1µF

V

CC

SHDN*

T_ OUT

T_ IN

GND

V

CC

0V

7k

150pF

MAX3222
MAX3232
MAX3237
MAX3241

5k

R_ IN

R_ OUT

EN

*

C2-

C2+

C1-

C1+

V-

V+

V

CC

C4

C3

C1

C2

0.1µF

V

CC

SHDN*

T_ OUT

T_ IN

GND

V

CC

0V

3k

2500pF

MINIMUM SLEW-RATE TEST CIRCUIT MAXIMUM SLEW-RATE TEST CIRCUIT

* MAX3222/MAX3241 ONLY

Figure 1. Slew-Rate Test Circuits

LapLink is a trademark of Traveling Software.

MAX3222/MAX3232/MAX3237/MAX3241

3.0V to 5.5V, Low-Power, up to 1Mbps, True RS-232
Transceivers Using Four 0.1µF External Capacitors

8 _______________________________________________________________________________________

RS-232 Receivers

The receivers convert RS-232 signals to CMOS-logic out­put levels. The MAX3222/MAX3237/MAX3241 receivers
have inverting three-state outputs. In shutdown, the
receivers can be active or inactive (Table 1).

The complementary outputs on the MAX3237 (R1OUTB)
and the MAX3241 (R1OUTB, R2OUTB) are always active,
regardless of the state of EN or SHDN. This allows for
Ring Indicator applications without forward biasing other
devices connected to the receiver outputs. This is ideal
for systems where VCCis set to 0V in shutdown to
accommodate peripherals, such as UARTs (Figure 2).

MAX3222/MAX3237/MAX3241

Shutdown Mode

Supply current falls to less than 1µA in shutdown mode
(SHDN = low). When shut down, the device’s charge
pumps are turned off, V+ is pulled down to VCC, V- is
pulled to ground, and the transmitter outputs are dis­abled (high impedance). The time required to exit shut­down is typically 100µs, as shown in Figure 3. Connect
SHDN to VCCif the shutdown mode is not used. SHDN
has no effect on R_OUT or R_OUTB.

MAX3222/MAX3237/MAX3241

Enable Control

The inverting receiver outputs (R_OUT) are put into a
high-impedance state when EN is high. The complemen­tary outputs R1OUTB and R2OUTB are always active,
regardless of the state of EN and SHDN (Table 1). EN
has no effect on T_OUT.

__________Applications Information

Capacitor Selection

The capacitor type used for C1–C4 is not critical for
proper operation; polarized or nonpolarized capacitors
can be used. The charge pump requires 0.1µF capaci­tors for 3.3V operation. For other supply voltages, refer to
Table 2 for required capacitor values. Do not use values
lower than those listed in Table 2. Increasing the capaci­tor values (e.g., by a factor of 2) reduces ripple on the
transmitter outputs and slightly reduces power consump­tion. C2, C3, and C4 can be increased without changing
C1’s value. However, do not increase C1 without also
increasing the values of C2, C3, and C4, to maintain the
proper ratios (C1 to the other capacitors).

When using the minimum required capacitor values,
make sure the capacitor value does not degrade exces­sively with temperature. If in doubt, use capacitors with a
higher nominal value. The capacitor’s equivalent series
resistance (ESR), which usually rises at low tempera­tures, influences the amount of ripple on V+ and V-.

MAX3237
MAX3241

T1OUT

R1OUTB

Tx

5k

UART

V

CC

T1IN

LOGIC

TRANSITION

DETECTOR

R1IN

R1OUT

EN = V

CC

SHDN = GND

V

CC

TO

µP

Rx

PREVIOUS

RS-232

Tx

UART

PROTECTION

DIODE

PROTECTION

DIODE

SHDN = GND

V

CC

V

CC

GND

Rx

5k

a) OLDER RS-232: POWERED-DOWN UART DRAWS CURRENT FROM
ACTIVE RECEIVER OUTPUT IN SHUTDOWN.

b) NEW MAX3237/MAX3241: EN SHUTS DOWN RECEIVER OUTPUTS (EXCEPT FOR

B OUTPUTS), SO NO CURRENT FLOWS TO UART IN SHUTDOWN. B OUTPUTS
INDICATE RECEIVER ACTIVITY DURING SHUTDOWN WITH EN HIGH.

GND

Figure 2. Detection of RS-232 Activity when the UART and
Interface are Shut Down; Comparison of MAX3237/MAX3241
(b) with Previous Transceivers (a).

MAX3222/MAX3232/MAX3237/MAX3241

3.0V to 5.5V, Low-Power, up to 1Mbps, True RS-232

Transceivers Using Four 0.1µF External Capacitors

_______________________________________________________________________________________ 9

Power-Supply Decoupling

In most circumstances, a 0.1µF bypass capacitor is
adequate. In applications that are sensitive to power­supply noise, decouple VCCto ground with a capacitor
of the same value as charge-pump capacitor C1. Connect
bypass capacitors as close to the IC as possible.

Operation Down to 2.7V

Transmitter outputs will meet EIA/TIA-562 levels of
±3.7V with supply voltages as low as 2.7V.

Transmitter Outputs when

Exiting Shutdown

Figure 3 shows two transmitter outputs when exiting
shutdown mode. As they become active, the two trans­mitter outputs are shown going to opposite RS-232 lev­els (one transmitter input is high, the other is low).
Each transmitter is loaded with 3kΩ in parallel with
2500pF. The transmitter outputs display no ringing or
undesirable transients as they come out of shutdown.
Note that the transmitters are enabled only when the
magnitude of V- exceeds approximately 3V.

Mouse Driveability

The MAX3241 has been specifically designed to power
serial mice while operating from low-voltage power sup­plies. It has been tested with leading mouse brands from
manufacturers such as Microsoft and Logitech. The
MAX3241 successfully drove all serial mice tested and
met their respective current and voltage requirements.
Figure 4a shows the transmitter output voltages under
increasing load current at 3.0V. Figure 4b shows a typical
mouse connection using the MAX3241.

Table 1. MAX3222/MAX3237/MAX3241
Shutdown and Enable Control Truth Table

Table 2. Required Minimum Capacitor Values

5V/div

V

CC

= 3.3V

C1–C4 = 0.1µF

2V/div

T2

50µs/div

T1

Figure 3. Transmitter Outputs when Exiting Shutdown or
Powering Up

V

CC

(V)

C1

(µF)

4.5 to 5.5 0.047

3.0 to 5.5 0.1

C2, C3, C4

(µF)

MAX3222/MAX3232/MAX3241

0.33

0.47

1 Active

0

1

Active1

SSHHDDNN

High-Z10

High-Z00

T_OUT

EENN

High-Z

Active

High-Z

Active

R_OUT

R_OUTB

(MAX3237/

MAX3241)

Active
Active
Active
Active

3.0 to 3.6 0.22

3.15 to 3.6 0.1

MAX3237

0.22

0.1

4.5 to 5.5 0.047

3.0 to 5.5 0.22

0.33

1.0

3.0 to 3.6 0.1 0.1

MAX3222/MAX3232/MAX3237/MAX3241

3.0V to 5.5V, Low-Power, up to 1Mbps, True RS-232
Transceivers Using Four 0.1µF External Capacitors

10 ______________________________________________________________________________________

MAX3241

EN

23

R5OUT

15

R4OUT

16

R3OUT

17

R2OUT

18

R1OUT

19

R2OUTB

20

R1OUTB

21

5k

5k

5k

5k

5k

R5IN 8

R4IN

7

6

R2IN 5

R1IN 4

SHDN

22

GND

25

T3IN

12

T2IN

13

T1IN

14

C2-

2

C2+

1

C1-

24

C1+

28

T3OUT

11

+V

COMPUTER SERIAL PORT

MOUSE

+V

-V

GND

Tx

T2OUT

10

T1OUT

9

V-

3

V+

27

V

CC

V

CC

C4

C3 C

1

C

2

0.1µF

V

CC

= 3V

to 5.5V

26

R3IN

Figure 4b. Mouse Driver Test Circuit

-6

-5

-4

-3

-2

-1

0

1

2

3

4

5

6

01234567

MAX3222-04

LOAD CURRENT PER TRANSMITTER (mA)

TRANSMITTER OUTPUT VOLTAGE (V)

V

OUT

+

VCC = 3.0V

V

OUT

-

V

OUT

+

V

CC

V

OUT

-

T1

T2

T3

Figure 4a. MAX3241 Transmitter Output Voltage vs. Load Current per Transmitter

MAX3222/MAX3232/MAX3237/MAX3241

3.0V to 5.5V, Low-Power, up to 1Mbps, True RS-232

Transceivers Using Four 0.1µF External Capacitors

______________________________________________________________________________________ 11

High Data Rates

The MAX3222/MAX3232/MAX3241 maintain the RS-232
±5.0V minimum transmitter output voltage even at high
data rates. Figure 5 shows a transmitter loopback test
circuit. Figure 6 shows a loopback test result at
120kbps, and Figure 7 shows the same test at 235kbps.
For Figure 6, all transmitters were driven simultaneously
at 120kbps into RS-232 loads in parallel with 1000pF.
For Figure 7, a single transmitter was driven at 235kbps,
and all transmitters were loaded with an RS-232 receiver
in parallel with 1000pF.

The MAX3237 maintains the RS-232 ±5.0V minimum
transmitter output voltage at data rates up to 1Mbps.
Figure 8 shows a loopback test result at 1Mbps with
MBAUD = VCC. For Figure 8, all transmitters were
loaded with an RS-232 receiver in parallel with 250pF.

MAX3222
MAX3232
MAX3237
MAX3241

5k

R_ IN

R_ OUT

EN

*

C2-

C2+

C1-

C1+

V-

V+

V

CC

C4

C3

C1

C2

0.1µF

V

CC

SHDN*

T_ OUT

T_ IN

GND

V

CC

0V

1000pF

* MAX3222/MAX3241 ONLY

Figure 5. Loopback Test Circuit

Figure 6. MAX3241 Loopback Test Result at 120kbps

T1IN

R1OUT

V

CC

= 3.3V

T1OUT

5V/div

5V/div

2µs/div

5V/div

Figure 7. MAX3241 Loopback Test Result at 235kbps

+5V

0V

+5V

0V

-5V
+5V

0V

T_IN

T_OUT = R_IN
5k + 250pF

R_OUT
150pF

200ns/div

VCC = 3.3V

Figure 8. MAX3237 Loopback Test Result at 1000kbps
(MBAUD = V

CC

)

T1IN

T1OUT

R1OUT

5µs/div

= 3.3V

V

CC

5V/div

5V/div

5V/div

MAX3222/MAX3232/MAX3237/MAX3241

3.0V to 5.5V, Low-Power, up to 1Mbps, True RS-232
Transceivers Using Four 0.1µF External Capacitors

12 ______________________________________________________________________________________

__________________________________________________Typical Operating Circuits

MAX3222

R2OUT10

1

R1OUT13

R2IN

9

18

GND

16

RS-232
OUTPUTS

TTL/CMOS

INPUTS

T2IN

11

T1IN

12

C2-

6

C2+

5

C1-

4

C1+

2

R1IN

14

T2OUT

8

T1OUT

15

V-

7

V+

3

V

CC

17

C1

0.1µF

C2

0.1µF

0.1µF

+3.3V

RS-232
INPUTS

TTL/CMOS

OUTPUTS

5k

5k

EN

SHDN

C3*

0.1µF

C4

0.1µF

PIN NUMBERS REFER TO DIP/SO PACKAGES.

* C3 CAN BE RETURNED TO EITHER V

CC

OR GROUND.

MAX3232

R2OUT9

R1OUT12

R2IN

8

GND

15

RS-232
OUTPUTS

TTL/CMOS

INPUTS

T2IN

10

T1IN

11

C2-

5

C2+

4

C1-

3

C1+

1

R1IN

13

T2OUT

7

T1OUT

14

V-

6

V+

2

V

CC

C4

0.1µF

16

0.1µF

0.1µF

0.1µF

+3.3V

RS-232
INPUTS

TTL/CMOS

OUTPUTS

C3*

0.1µF

5k

5k

* C3 CAN BE RETURNED TO EITHER V

CC

OR GROUND.

SEE TABLE 2 FOR CAPACITOR SELECTION

Interconnection with 3V and 5V Logic

The MAX3222/MAX3232/MAX3237/MAX3241 can
directly interface with various 5V logic families, includ­ing ACT and HCT CMOS. See Table 3 for more informa­tion on possible combinations of interconnections.

Table 3. Logic-Family Compatibility
with Various Supply Voltages

Compatible with ACT and
HCT CMOS, and with TTL.
Incompatible with AC, HC,
and CD4000 CMOS.

3.35

SYSTEM
POWER­SUPPLY

VOLTAGE

(V)

Compatible with all TTL
and CMOS-logic families.

55

Compatible with all CMOS
families.

3.33.3

COMPATIBILITY

MAX32_ _

V

CC

SUPPLY

VOLTAGE

(V)

MAX3222/MAX3232/MAX3237/MAX3241

3.0V to 5.5V, Low-Power, up to 1Mbps, True RS-232

Transceivers Using Four 0.1µF External Capacitors

______________________________________________________________________________________ 13

_____________________________________Typical Operating Circuits (continued)

MAX3241

EN

23

R5OUT

15

R4OUT

16

R3OUT

17

R2OUT

18

R1OUT

19

R2OUTB

20

R1OUTB

21

TTL/CMOS

OUTPUTS

5k

5k

5k

5k

5k

R5IN 8

* C3 CAN BE RETURNED TO EITHER V

CC

OR GROUND.

R4IN

7

R3IN

6

R2IN 5

R1IN

4

RS-232
INPUTS

SHDN

22

GND

25

RS-232
OUTPUTS

TTL/CMOS

INPUTS

T3IN

12

T2IN

13

T1IN

14

C2-

2

C2+

1

C1-

24

C1+

28

T3OUT

11

T2OUT 10

T1OUT 9

V-

3

V+

27

V

CC

C4

0.1µF

C3

*

0.1µF

0.1µF

0.1µF

0.1µF

+3.3V

26

0.1µF

0.1µF

0.1µF

LOGIC

INPUTS

LOGIC

OUTPUTS

26

V

28

C1+

25

C1-

1

C2+

3

C2­T1IN

24

T2IN

23

T3IN

22

T4IN

19

T5IN

17

R1OUTB

16

R1OUT

21

R2OUT

20

R3OUT

18

CC

MAX3237

T1

T2

T3

T4

T5

R1

R2

R3

V+

V-

T1OUT 5

T2OUT 6

T3OUT

T4OUT 10

T5OUT

R1IN

5k

R2IN 9

5k

R3IN

5k

0.1µF

27

4

0.1µF

7

RS-232
OUTPUTS

12

8

RS-232
INPUTS

11

15

2

MBAUD

SHDN

OR GROUND.

CC

14

EN

13

GND

* C3 CAN BE RETURNED TO EITHER V

MAX3222/MAX3232/MAX3237/MAX3241

3.0V to 5.5V, Low-Power, up to 1Mbps, True RS-232
Transceivers Using Four 0.1µF External Capacitors

14 ______________________________________________________________________________________

_____________________________________________Pin Configurations (continued)

16
15
14
13
12
11
10

9

1
2
3
4
5
6
7
8

V

CC

GND
T1OUT
R1INC2+

C1-

V+

C1+

MAX3232

R1OUT
T1IN
T2IN
R2OUTR2IN

T2OUT

V-

C2-

DIP/SO/TSSOP

TOP VIEW

20
19
18
17
16
15
14
13

1
2
3

8

12
11

10

4
5
6
7

SHDN
V

CC

GND
T1OUT

C1-

V+

C1+

EN

R1IN
R1OUT

T1IN
T2IN

T2OUT

V-

C2-

C2+

9

R2IN

R2OUT

SSOP/TSSOP

N.C.

N.C.

MAX3222

28
27
26
25
24
23
22
21
20
19
18
17
16

15

1
2
3
4
5
6
7
8

9
10
11
12
13
14

C1+
V+
V

CC

C1­T1IN

T2IN

MBAUD

T3IN
R1OUT
R2OUT
T4IN
R3OUT
T5IN
R1OUTB

SHDN

EN

T5OUT

R3IN

T4OUT

R2IN

R1IN

T3OUT

T2OUT

T1OUT

V-

C2-

GND

C2+

SSOP

MAX3237

28
27
26
25
24
23
22
21
20
19
18
17
16
15

1
2
3
4
5
6
7
8

9
10
11
12
13
14

C1+
V+
V

CC

GND

C1-

EN

R5OUT

SHDN
R1OUTB

R2OUTB

R1OUT
R2OUT
R3OUT
R4OUT

T1IN

T2IN

T3IN

T3OUT

T2OUT

T1OUT

R5IN

R4IN

R3IN

R2IN

R1IN

V-

C2-

C2+

SO/SSOP/TSSOP

MAX3241

MAX3222/MAX3232/MAX3237/MAX3241

3.0V to 5.5V, Low-Power, up to 1Mbps, True RS-232

Transceivers Using Four 0.1µF External Capacitors

______________________________________________________________________________________ 15

______3V-Powered EIA/TIA-232 and EIA/TIA-562 Transceivers from Maxim

Ordering Information (continued)

* Dice are tested at TA= +25°C, DC parameters only.

0.1µF capacitors, 1 complemen­tary receiver, MegaBaud
operation

232250/100035/33.0 to 5.5MAX3237

0.1µF capacitors, AutoShutdown,
complementary receiver,
drives mice

23212013/53.0 to 5.5MAX3243

0.1µF capacitors232120N/A2/23.0 to 5.5MAX3232

0.1µF capacitors, AutoShutdown23212022/23.0 to 5.5MAX3223

0.1µF capacitors23212022/23.0 to 5.5MAX3222

232

562

232
562

232

EIA/

TIA-232

OR 562

2.7 to 3.6

AutoShutdown, complementary
receiver, drives mice, transient
detection

23553/5MAX3212

0.1µF capacitors23022/23.0 to 3.6MAX563

Operates directly from batteries
without a voltage regulator

12022/21.8 to 4.25MAX218

No. OF

RECEIVERS

ACTIVE IN

SHUTDOWN

POWER-

SUPPLY

VOLTAGE

(V)

Wide supply range23053/52.7 to 5.25MAX562

Drives mice12053/53.0 to 3.6MAX212

FEATURES

GUAR-

ANTEED

DATA
RATE

(kbps)

No. OF

TRANSMITTERS/

RECEIVERS

PART

0.1µF capacitors, 2 complemen­tary receivers, drives mice

23212053/53.0 to 5.5MAX3241

PART

MAX3222EUP
MAX3222EAP
MAX3222EWN -40°C to +85°C

-40°C to +85°C

-40°C to +85°C

TEMP. RANGE PIN-PACKAGE

20 TSSOP
20 SSOP
18 SO

MAX3222EPN

MAX3232CUE
MAX3232CSE 0°C to +70°C

0°C to +70°C

-40°C to +85°C 18 Plastic DIP

16 TSSOP
16 Narrow SO

MAX3232CWE

MAX3232EUE
MAX3232ESE -40°C to +85°C

-40°C to +85°C

0°C to +70°C 16 Wide SO

16 TSSOP
16 Narrow SO

MAX3222C/D 0°C to +70°C Dice*

MAX3232CPE 0°C to +70°C 16 Plastic DIP

PART TEMP. RANGE PIN-PACKAGE

MAX3232EWE

MAX3237CAI
MAX3237EAI -40°C to +85°C

0°C to +70°C

-40°C to +85°C 16 Wide SO

28 SSOP
28 SSOP

MAX3241CUI

0°C to +70°C 28 TSSOP

MAX3241CAI

MAX3241EUI
MAX3241EAI -40°C to +85°C

-40°C to +85°C

0°C to +70°C 28 SSOP

28 TSSOP
28 SSOP

MAX3241EWI -40°C to +85°C 28 SO

MAX3241CWI 0°C to +70°C 28 SO

MAX3232EPE -40°C to +85°C 16 Plastic DIP

MAX3222/MAX3232/MAX3237/MAX3241

3.0V to 5.5V, Low-Power, up to 1Mbps, True RS-232
Transceivers Using Four 0.1µF External Capacitors

Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are
implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.

16

____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600

© 1999 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.

___________________Chip Topography

___________________Chip Information

________________________________________________________Package Information

T1INT2IN

0.127"

(3.225mm)

0.087"

(2.209mm)

R2OUTR2INT2OUT

R1OUT

R1IN

T1OUT

V

CC

V+ C1+

SHDN

EN

C1-

C2+

C2-

V-

GND

MAX3222

TRANSISTOR COUNT: 339
SUBSTRATE CONNECTED TO GND

MAX3222 339
MAX3232 339
MAX3237 1212
MAX3241 894

TRANSISTOR COUNTPART

TSSOP.EPS