General Description
The MAX3222/MAX3232/MAX3237/MAX3241 transceiv-
ers 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 charge-pump 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 normal operating mode and 1Mbps in
the MegaBaud™ operating mode.
The MAX3222/MAX3232 have 2 receivers and 2 drivers.
The MAX3222 and MAX3232 are pin, package, and func-
tionally compatible with the industry-standard MAX242
and MAX232, respectively.
The MAX3241 has 5 receivers and 3 drivers, while the
MAX3237 has 3 receivers and 5 drivers. 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 to be
monitored without forward biasing the protection diodes in
circuitry that may have VCC completely removed.
The MAX3222, MAX3232, and MAX3241 are available in
space-saving TSSOP and SSOP packages with operating
temperatures of either -40°C to +85°C or 0°C to 70°C.
Applications
●Battery-Powered Equipment
●Hand-Held Equipment
●Peripherals
●Datacom Equipment
Benefits and Features
●Integrated Features Saves Board Space and
Simplifies Design
• Charge Pump Circuitry Eliminates the Need for a
Bipolar ±12V Supply
• Wide Single-Supply Operation From +3V to +5.5V
Supply
• Always-On Extra Outputs Enable Monitoring of
External Devices
●Power Saving Extends Battery Life
• 1µA Supply Current in Shutdown Mode While
Receiver is Active (MAX3222, MAX3237,
MAX3241)
Ordering Information continued at end of data sheet.
Typical Operating Circuits appear at end of data sheet. Pin Configurations continued at end of data sheet.
MegaBaud and UCSP are trademarks of Maxim Integrated Products, Inc.
*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.
19-0273; Rev 8; 6/18
+Denotes lead-free package.
PART TEMP RANGE PIN-
PACKAGE
PKG
CODE
MAX3222CUP+ 0°C to +70°C 20 TSSOP U20+2
MAX3222CAP+ 0°C to +70°C 20 SSOP A20+1
MAX3222CWN+ 0°C to +70°C 18 SO W18+1
MAX3222CPN+ 0°C to +70°C 18 Plastic Dip P18+5
Ordering Information
Pin Congurations
18
17
16
15
14
13
12
11
1
2
3
4
5
6
7
8
SHDN
VCC
GND
T1OUT
C1-
V+
C1+
EN
TOP VIEW
R1IN
R1OUT
T1IN
T2IN
T2OUT
V-
C2-
C2+
10
9R2OUTR2IN
DIP/SO
MAX3222
Click here for production status of specic part numbers.
MAX3222/MAX3232/
MAX3237/MAX3241*
3.0V to 5.5V, Low-Power, Up to 1Mbps,
True RS-232 Transceivers
VCC ..........................................................................-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 (VCC + 0.3V)
R_IN.................................................................................±25V
Output Voltages
T_OUT ..........................................................................±13.2V
R_OUT .................................................. -0.3V to (VCC + 0.3V)
Short-Circuit Duration
T_OUT ...................................................................Continuous
Continuous Power Dissipation (TA = +70°C)
16-Pin TSSOP (derate 6.7mW/°C above +70°C) ........ 533mW
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 Plastic DIP (derate 10.53mW/°C above +70°C) ..842mW
18-Pin SO (derate 9.52mW/°C above +70°C) ............. 762mW
18-Pin Plastic DIP (derate 11.11mW/°C above +70°C) ...889mW
20-Pin SSOP (derate 7.00mW/°C above +70°C) ........559mW
20-Pin TSSOP (derate 8.0mW/°C above +70°C) ........ 640mW
28-Pin TSSOP (derate 8.7mW/°C above +70°C) ........ 696mW
28-Pin SSOP (derate 9.52mW/°C above +70°C) ........762mW
28-Pin SO (derate 12.50mW/°C above +70°C) .................. 1W
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, 10s) ................................. +300°C
(VCC = +3.0V to +5.5V, C1–C4 = 0.1μF (Note 2), TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25°C.)
Note 1: V+ and V- can have a maximum magnitude of 7V, but their absolute difference cannot exceed 13V.
PARAMETER CONDITIONS MIN TYP MAX UNITS
DC CHARACTERISTICS
VCC Power-Supply Current No load, VCC = 3.3V or 5.0V,
TA = +25°C
MAX3222/MAX3232/
MAX3241 0.3 1.0 mA
MAX3237 0.5 2.0
Shutdown Supply Current SHDN = GND, TA = +25°C 1.0 10 µA
LOGIC INPUTS AND RECEIVER OUTPUTS
Input Logic Threshold Low
(Note 3) T_IN, EN, SHDN, MBAUD 0.8 V
Input Logic Threshold High
(Note 3)
VCC = 3.3V 2.0 V
VCC = 5.0V 2.4
Input Leakage Current T_IN, EN, SHDN, MBAUD ±0.01 ±1.0 µA
Output Leakage Current Receivers disabled ±0.05 ±10 µA
Output Voltage Low IOUT = 1.6mA 0.4 V
Output Voltage High IOUT = -1.0mA VCC -
0.6
VCC
- 0.1 V
RECEIVER INPUTS
Input Voltage Range -25 25 V
Input Threshold Low TA = +25°C VCC = 3.3V 0.6 1.2 V
VCC = 5.0V 0.8 1.5
Input Threshold High TA = +25°C VCC = 3.3V 1.5 2.4 V
VCC = 5.0V 1.8 2.4
Absolute Maximum Ratings
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.
Electrical Characteristics
MAX3222/MAX3232/
MAX3237/MAX3241
3.0V to 5.5V, Low-Power, Up to 1Mbps,
True RS-232 Transceivers
www.maximintegrated.com Maxim Integrated
│
2
(VCC = +3.0V to +5.5V, C1–C4 = 0.1μF (Note 2), TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25°C.)
(VCC = +3.0V to +5.5V, C1–C4 = 0.1μF (Note 2), TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25°C.)
PARAMETER CONDITIONS MIN TYP MAX UNITS
Input Hysteresis 0.3 V
Input Resistance TA = +25°C 3 5 7 kΩ
TRANSMITTER OUTPUTS
Output Voltage Swing All transmitter outputs loaded with 3kΩ to ground ±5.0 ±5.4 V
Output Resistance VCC = V+ = V- = 0V, VOUT = ±2V 300 10M Ω
Output Short-Circuit Current ±35 ±60 mA
Output Leakage Current VOUT = ±12V, VCC = 0V or 3V to 5.5V, transmitters
disabled ±25 µA
MOUSE DRIVEABILITY (MAX3241)
Transmitter Output Voltage
T1IN = T2IN = GND, T3IN = VCC,
T3OUT loaded with 3kΩ to GND,
T1OUT and T2OUT loaded with 2.5mA each
±5.0 V
PARAMETER CONDITIONS MIN TYP MAX UNITS
Maximum Data Rate RL = 3kΩ, CL = 1000pF, one transmitter switching 120 235 kbps
Receiver Propagation Delay R_IN to R_OUT, CL = 150pF tPHL 0.3 μs
tPLH 0.3
Receiver Output Enable Time Normal operation 200 ns
Receiver Output Disable Time Normal operation 200 ns
Transmitter Skew | tPHL - tPLH | 300 ns
Receiver Skew | tPHL - tPLH | 300 ns
Transition-Region Slew Rate
VCC = 3.3V, RL = 3kΩ to 7kΩ,
+3V to -3V or -3V to +3V,
TA = +25°C, one transmitter
switching
CL = 150pF to
1000pF 6 30
V/μs
CL = 150pF to
2500pF 4 30
Timing Characteristics—MAX3222/MAX3232/MAX3241
Electrical Characteristics (continued)
MAX3222/MAX3232/
MAX3237/MAX3241
3.0V to 5.5V, Low-Power, Up to 1Mbps,
True RS-232 Transceivers
www.maximintegrated.com Maxim Integrated
│
3
(VCC = +3.0V to +5.5V, C1–C4 = 0.1μF (Note 2), TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25°C.)
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.
(VCC = +3.3V, 235kbps data rate, 0.1μF capacitors, all transmitters loaded with 3kΩ, TA = +25°C, unless otherwise noted.)
PARAMETER CONDITIONS MIN TYP MAX UNITS
Maximum Data Rate
RL = 3kΩ, CL = 1000pF, one transmitter switching,
MBAUD = GND 250
kbps
VCC = 3.0V to 4.5V, RL = 3kΩ, CL = 250pF,
one transmitter switching, MBAUD = VCC
1000
VCC = 4.5V to 5.5V, RL = 3kΩ, CL = 1000pF,
one transmitter switching, MBAUD = VCC
1000
Receiver Propagation Delay R_IN to R_OUT, CL = 150pF tPHL 0.15 µs
tPLH 0.15
Receiver Output Enable Time Normal operation 200 ns
Receiver Output Disable Time Normal operation 200 ns
Transmitter Skew | tPHL - tPLH |, MBAUD = GND 100 ns
| tPHL - tPLH |, MBAUD = VCC 25 ns
Receiver Skew | tPHL - tPLH | 50 ns
Transition-Region Slew Rate
VCC = 3.3V, RL = 3Ω to 7kΩ,
+3V to -3V or -3V to +3V,
TA = +25°C
CL = 150pF
to 1000pF
MBAUD =
GND 6 30
V/μs
MBAUD =
VCC
24 150
CL = 150pF to 2500pF,
MBAUD = GND 4 30
Timing Characteristics—MAX3237
Typical Operating Characteristics
-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
VOUT+
VOUT-
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
MAX3222/MAX3232/
MAX3237/MAX3241
3.0V to 5.5V, Low-Power, Up to 1Mbps,
True RS-232 Transceivers
www.maximintegrated.com Maxim Integrated
│
4
(VCC = +3.3V, 235kbps data rate, 0.1μF capacitors, all transmitters loaded with 3kΩ, TA = +25°C, unless otherwise noted.)
Typical Operating Characteristics (continued)
0
10
20
30
50
40
60
70
0
MAX3237
SLEW RATE vs. LOAD CAPACITANCE
(MBAUD = VCC)
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 + CL LOAD EACH OUTPUT
VCC = 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 = GND)
MAX3222-07
LOAD CAPACITANCE (pF)
TRANSMITTER OUTPUT VOLTAGE (V)
2000 30001000 4000 5000
1 TRANSMITTER AT 240kbps
4 TRANSMITTERS AT 15kbps
3kΩ + CL LOADS
VCC = 3.3V
-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
VOUT+
1 TRANSMITTER AT 235kbps
2 TRANSMITTERS AT 30kbps
VOUT-
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
20kbps
1 TRANSMITTER AT FULL DATA RATE
4 TRANSMITTERS AT 1/16 DATA RATE
3kΩ + CL LOADS
VCC = 3.3V
120kbps
-7.5
-5.0
-2.5
0
2.5
5.0
7.5
0
MAX3237
TRANSMITTER OUTPUT VOLTAGE
vs. LOAD CAPACITANCE (MBAUD = VCC)
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 + CL LOAD, EACH OUTPUT
VCC = 3.3V
2Mbps 1.5Mbps
1Mbps
2Mbps
1Mbps
1.5Mbps
4
6
8
10
12
14
16
18
20
22
24
0
SLEW RATE
vs. LOAD CAPACITANCE
MAX3222-05
LOAD CAPACITANCE (pF)
SLEW RATE (V/µs)
2000 30001000 4000 5000
+SLEW
-SLEW
0
10
30
20
40
50
60
70
0
MAX3237
SKEW vs. LOAD CAPACITANCE
(tPLH - tPHL)
MAX3222-12
LOAD CAPACITANCE (pF)
1000 1500500 2000 2500
MAX
MIN
AVERAGE; 10 PARTS
1 TRANSMITTER AT 512kbps
4 TRANSMITTERS AT 32kbps
3kΩ + CL LOADS
VCC = 3.3V
MBAUD = VCC
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 + CL LOADS
VCC = 3.3V
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
MAX3222/MAX3232/
MAX3237/MAX3241
3.0V to 5.5V, Low-Power, Up to 1Mbps,
True RS-232 Transceivers
Maxim Integrated
│
5
www.maximintegrated.com
PIN
NAME FUNCTIONMAX3222 MAX3232 MAX3237 MAX3241
DIP/SO SSOP
1 1 — 13 23 EN Receiver Enable. Active low.
2 2 1 28 28 C1+ Positive Terminal of Voltage-Doubler Charge-Pump
Capacitor
3 3 2 27 27 V+ +5.5V Generated by the Charge Pump
4 4 3 25 24 C1- Negative Terminal of Voltage-Doubler Charge-Pump
Capacitor
5 5 4 1 1 C2+ Positive Terminal of Inverting Charge-Pump Capacitor
6 6 5 3 2 C2- Negative Terminal of Inverting Charge-Pump Capacitor
7 7 6 4 3 V- -5.5V Generated by the Charge Pump
8, 15 8, 17 7, 14 5, 6, 7,
10, 12 9, 10, 11 T_OUT RS-232 Transmitter Outputs
9, 14 9, 16 8, 13 8, 9, 11 4–8 R_IN RS-232 Receiver Inputs
10, 13 10, 15 9, 12 18, 20, 21 15–19 R_OUT TTL/CMOS Receiver Outputs
11, 12 12, 13 10, 11 17, 19, 22,
23, 24 12, 13, 14 T_IN TTL/CMOS Transmitter Inputs
16 18 15 2 25 GND Ground
17 19 16 26 26 VCC +3.0V to +5.5V Supply Voltage
18 20 — 14 22 SHDN Shutdown Control. Active low.
— 11, 14 — — — N.C. No Connection
— — — 15 — MBAUD
MegaBaud Control Input. Connect to GND for normal
operation; connect to VCC for 1Mbps transmission rates.
— — — 16 20, 21 R_OUTB Noninverting Complementary Receiver Outputs.
Always active.
Pin Description
MAX3222/MAX3232/
MAX3237/MAX3241
3.0V to 5.5V, Low-Power, Up to 1Mbps,
True RS-232 Transceivers
Maxim Integrated
│
6
www.maximintegrated.com
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 guar-
antee a 120kbps data rate with worst-case loads of
3kΩ in parallel with 1000pF, providing compatibility with
PC-to-PC 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 shut-
down 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 pullup resistors.
Connect unused inputs to GND or VCC.
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 guar-
antee a 1Mbps data rate with worst-case loads of 3kΩ in
parallel with 250pF for 3.0V < VCC < 4.5V. For 5V ±10%
operation, the MAX3237 transmitters guarantee a 1Mbps
data rate into worst-case loads of 3kΩ in parallel with
1000pF.
LapLink is a trademark of Traveling Software, Inc.
Figure 1. Slew-Rate Test Circuits
MAX3222
MAX3232
MAX3237
MAX3241
5kΩ
R_ IN
R_ OUT
EN*
C2-
C2+
C1-
C1+
V-
V+
VCC
C4
C3
C1
C2
0.1µF
VCC
SHDN*
T_ OUT
T_ IN
GND
VCC
0V
7kΩ150pF
MAX3222
MAX3232
MAX3237
MAX3241
5kΩ
R_ IN
R_ OUT
EN*
C2-
C2+
C1-
C1+
V-
V+
VCC
C4
C3
C1
C2
0.1µF
VCC
SHDN*
T_ OUT
T_ IN
GND
VCC
0V
3kΩ2500pF
MINIMUM SLEW-RATE TEST CIRCUIT MAXIMUM SLEW-RATE TEST CIRCUIT
*MAX3222/MAX3237/MAX3241 ONLY
MAX3222/MAX3232/
MAX3237/MAX3241
3.0V to 5.5V, Low-Power, Up to 1Mbps,
True RS-232 Transceivers
www.maximintegrated.com Maxim Integrated
│
7
RS-232 Receivers
The receivers convert RS-232 signals to CMOS-logic
output levels. The MAX3222/MAX3237/MAX3241 receiv-
ers 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 VCC is 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 VCC if 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 complemen-
tary 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 capaci-
tors 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 trans-
mitter 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 increas-
ing 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 exces-
sively with temperature. If in doubt, use capacitors with a
higher nominal value. The capacitor’s equivalent series
resistance (ESR), which usually rises at low tempera-
tures, influences the amount of ripple on V+ and V-.
Figure 2. Detection of RS-232 Activity when the UART and
Interface are Shut Down; Comparison of MAX3237/MAX3241
(b) with Previous Transceivers (a).
MAX3237
MAX3241
T1OUT
R1OUTB
Tx
5kΩ
UART
VCC
T1IN
LOGIC
TRANSITION
DETECTOR
R1IN
R1OUT
EN = VCC
SHDN = GND
VCC
TO
µP
Rx
PREVIOUS
RS-232
Tx
UART
PROTECTION
DIODE
PROTECTION
DIODE
SHDN = GND
VCC
VCC
GND
Rx
5kΩ
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
MAX3222/MAX3232/
MAX3237/MAX3241
3.0V to 5.5V, Low-Power, Up to 1Mbps,
True RS-232 Transceivers
www.maximintegrated.com Maxim Integrated
│
8
Power-Supply Decoupling
In most circumstances, a 0.1μF bypass capacitor is
adequate. In applications that are sensitive to power-
supply noise, decouple VCC to 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 shut-
down 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 transmit-
ter is loaded with 3kΩ in parallel with 2500pF. The trans-
mitter 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 sup-
plies. 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
Figure 3. Transmitter Outputs when Exiting Shutdown or
Powering Up
SHDN EN T_OUT R_OUT
R_OUTB
(MAX3237/
MAX3241)
0 0 High-Z Active Active
0 1 High-Z High-Z Active
1 0 Active Active Active
1 1 Active High-Z Active
VCC
(V)
C1
(µF)
C2, C3, C4
(µF)
MAX3222/MAX3232/MAX3241
3.0 to 3.6 0.1 0.1
4.5 to 5.5 0.047 0.33
3.0 to 5.5 0.1 0.47
MAX3237
3.0 to 3.6 0.22 0.22
3.15 to 3.6 0.1 0.1
4.5 to 5.5 0.047 0.33
3.0 to 5.5 0.22 1.0
5V/div
VCC = 3.3V
C1–C4 = 0.1µF
2V/div
T2
50µs/div
T1
MAX3222/MAX3232/
MAX3237/MAX3241
3.0V to 5.5V, Low-Power, Up to 1Mbps,
True RS-232 Transceivers
www.maximintegrated.com Maxim Integrated
│
9
Figure 4a. MAX3241 Transmitter Output Voltage vs. Load Current per Transmitter
Figure 4b. Mouse Driver Test Circuit
-6
-5
-4
-3
-2
-1
0
1
2
3
4
5
6
0 1 2 3 4 5 6 7
MAX3222-04
LOAD CURRENT PER TRANSMITTER (mA)
TRANSMITTER OUTPUT VOLTAGE (V)
VOUT+
VCC = 3.0V
VOUT-
VOUT+
VCC VOUT-
T1
T2
T3
MAX3241
EN
23
R5OUT
15
R4OUT
16
R3OUT
17
R2OUT
18
R1OUT
19
R2OUTB
20
R1OUTB
21
5kΩ
5kΩ
5kΩ
5kΩ
5kΩ
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
VCC
VCC
C4
C3 C1
C2
0.1µF
VCC = 3V
to 5.5V
26
R3IN
MAX3222/MAX3232/
MAX3237/MAX3241
3.0V to 5.5V, Low-Power, Up to 1Mbps,
True RS-232 Transceivers
www.maximintegrated.com Maxim Integrated
│
10
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 transmit-
ters 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.
Figure 5. Loopback Test Circuit
Figure 6. MAX3241 Loopback Test Result at 120kbps
Figure 7. MAX3241 Loopback Test Result at 235kbps
Figure 8. MAX3237 Loopback Test Result at 1000kbps
(MBAUD = VCC)
MAX3222
MAX3232
MAX3237
MAX3241
5kΩ
R_ IN
R_ OUT
EN*
C2-
C2+
C1-
C1+
V-
V+
VCC
C4
C3
C1
C2
0.1µF
VCC
SHDN*
T_ OUT
T_ IN
GND
VCC
0V 1000pF
* MAX3222/MAX3241 ONLY
T1IN
R1OUT
VCC = 3.3V
T1OUT
5V/div
5V/div
5V/div
5µs/div
T1IN
R1OUT
VCC = 3.3V
T1OUT
5V/div
5V/div
2µs/div
5V/div
T_IN
T_OUT = R_IN
5kΩ + 250pF
R_OUT
150pF
VCC = 3.3V
200ns/div
+5V
0V
+5V
0V
-5V
+5V
0V
MAX3222/MAX3232/
MAX3237/MAX3241
3.0V to 5.5V, Low-Power, Up to 1Mbps,
True RS-232 Transceivers
www.maximintegrated.com Maxim Integrated
│
11
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
SYSTEM
POWER-
SUPPLY
VOLTAGE
(V)
MAX32_ _
VCC
SUPPLY
VOLTAGE
(V)
COMPATIBILITY
3.3 3.3 Compatible with all CMOS
families.
5 5 Compatible with all TTL
and CMOS-logic families
5 3.3
Compatible with ACT and
HCT CMOS, and with TTL.
Incompatible with AC, HC,
and CD4000 CMOS.
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
VCC
17
C1
0.1µF
C2
0.1µF
0.1µF
+3.3V
RS-232
INPUTS
TTL/CMOS
OUTPUTS 5kΩ
5kΩ
EN
SHDN
C3*
0.1µF
C4
0.1µF
PIN NUMBERS REFER TO DIP/SO PACKAGES.
* C3 CAN BE RETURNED TO EITHER VCC 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
VCC
C4
0.1µF
16
0.1µF
0.1µF
0.1µF
+3.3V
RS-232
INPUTS
TTL/CMOS
OUTPUTS
C3*
0.1µF
5kΩ
5kΩ
* C3 CAN BE RETURNED TO EITHER VCC OR GROUND.
SEE TABLE 2 FOR CAPACITOR SELECTION
MAX3222/MAX3232/
MAX3237/MAX3241
3.0V to 5.5V, Low-Power, Up to 1Mbps,
True RS-232 Transceivers
www.maximintegrated.com Maxim Integrated
│
12
Typical Operating Circuits (continued)
MAX3237
EN
13
R3OUT
18
R2OUT
20
R1OUT
21
R1OUTB
16
LOGIC
OUTPUTS
5kΩ
5kΩ
5kΩ
* C3 CAN BE RETURNED TO EITHER VCC OR GROUND.
R3IN 11
R2IN 9
R1IN 8
RS-232
INPUTS
GND
2
RS-232
OUTPUTS
LOGIC
INPUTS
T3IN
22
T2IN
23
T1IN
24
C2-
3
C2+
1
C1-
25
C1+
28
T3OUT 7
T2OUT 6
T1OUT 5
T1
T2
T3
R1
R2
R3
V- 4
V+
27
VCC
0.1µF
0.1µF
0.1µF
0.1µF
0.1µF
26
MBAUD 15
T5IN
17
T4IN
19
T5OUT 12
T4OUT 10
SHDN 14
T4
T5
MAX3241
EN
23
R5OUT
15
R4OUT
16
R3OUT
17
R2OUT
18
R1OUT
19
R2OUTB
20
R1OUTB
21
TTL/CMOS
OUTPUTS
5kΩ
5kΩ
5kΩ
5kΩ
5kΩ
R5IN 8
* C3 CAN BE RETURNED TO EITHER VCC 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
VCC
C4
0.1µF
C3*
0.1µF
0.1µF
0.1µF
0.1µF
+3.3V 26
MAX3222/MAX3232/
MAX3237/MAX3241
3.0V to 5.5V, Low-Power, Up to 1Mbps,
True RS-232 Transceivers
www.maximintegrated.com Maxim Integrated
│
13
Pin Congurations (continued)
16
15
14
13
12
11
10
9
1
2
3
4
5
6
7
8
VCC
GND
T1OUT
R1IN
C2+
C1-
V+
C1+
MAX3232
R1OUT
T1IN
T2IN
R2OUT
R2IN
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
VCC
GND
T1OUT
C1-
V+
C1+
R1IN
R1OUT
T1IN
T2IN
T2OUT
V-
C2-
C2+
9R2IN
R2OUT
SSOP/TSSOP
EN
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+
VCC
C1-
T1IN
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+
VCC
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
www.maximintegrated.com Maxim Integrated
│
14
*Dice are tested at TA = +25°C, DC parameters only.
+Denotes lead-free package.
PART TEMP RANGE PIN-
PACKAGE
PKG
CODE
MAX3222EUP+ -40°C to +85°C 20 TSSOP U20+2
MAX3222EAP+ -40°C to +85°C 20 SSOP A20+1
MAX3222EWN+ -40°C to +85°C 18 SO W18+1
MAX3222EPN+ -40°C to +85°C 18 Plastic Dip P18+5
MAX3222C/D 0°C to +70°C Dice* —
MAX3232CUE+ 0°C to +70°C 16 TSSOP U16+1
MAX3232CSE+ 0°C to +70°C 16 Narrow SO S16+1
MAX3232CWE+ 0°C to +70°C 16 Wide SO W16+1
MAX3232CPE+ 0°C to +70°C 16 Plastic DIP P16+1
MAX3232EUE+ -40°C to +85°C 16 TSSOP U16+1
MAX3232ESE+ -40°C to +85°C 16 Narrow SO S16+5
PART TEMP RANGE PIN-
PACKAGE
PKG
CODE
MAX3232EWE+ -40°C to +85°C 16 Wide SO W16+1
MAX3232EPE+ -40°C to +85°C 16 Plastic DIP P16+1
MAX3237CAI+ 0°C to +70°C 16 SSOP A28+2
MAX3237EAI+ -40°C to +85°C 28 SSOP A28+1
MAX3241CUI+ 0°C to +70°C 28 TSSOP U28+2
MAX3241CAI+ 0°C to +70°C 28 SSOP A28+1
MAX3241CWI+ 0°C to +70°C 28 SO W28+6
MAX3241EUI+ -40°C to +85°C 28 TSSOP U28+2
MAX3241EAI+ -40°C to +85°C 28 SSOP A28+1
MAX3241EWI+ -40°C to +85°C 28 SO W28+6
PART
POWER-
SUPPLY
VOLTAGE
(V)
NO. OF
TRANSMITTERS/
RECEIVERS
NO. OF
RECEIVERS
ACTIVE IN
SHUTDOWN
GUAR-
ANTEED
DATA
RATE
(kbps)
EIA/
TIA-232
OR 562
FEATURES
MAX212 3.0 to 3.6 3/5 5 120 232 Drives mice
MAX218 1.8 to 4.25 2/2 2 120 232 Operates directly from batteries
without a voltage regulator
MAX562 2.7 to 5.25 3/5 5 230 562 Wide supply range
MAX563 3.0 to 3.6 2/2 2 230 562 0.1μF capacitors
MAX3212 2.7 to 3.6 3/5 5 235 232
AutoShutdown, complementary
receiver, drives mice, transient
detection
MAX3222 3.0 to 5.5 2/2 2 120 232 0.1μF capacitors
MAX3223 3.0 to 5.5 2/2 2 120 232 0.1μF capacitors, AutoShutdown
MAX3232 3.0 to 5.5 2/2 N/A 120 232 0.1μF capacitors
MAX3237 3.0 to 5.5 5/3 3 250/1000 232 0.1μF capacitors, 1 complementary
receiver, MegaBaud operation
MAX3241 3.0 to 5.5 3/5 5 120 232 0.1μF capacitors, 2 complementary
receivers, drives mice
MAX3243 3.0 to 5.5 3/5 1 120 232
0.1μF capacitors, AutoShutdown,
complementary receiver,
drives mice
Ordering Information (continued)
3V-Powered EIA/TIA-232 and EIA/TIA-562 Transceivers from Maxim
MAX3222/MAX3232/
MAX3237/MAX3241
3.0V to 5.5V, Low-Power, Up to 1Mbps,
True RS-232 Transceivers
www.maximintegrated.com Maxim Integrated
│
15
PACKAGE
TYPE
PACKAGE
CODE
OUTLINE
NO.
LAND
PATTERN NO.
20 TSSOP
U20+2
21-0066 90-0116
20 SSOP
A20+1
21-0056 90-0094
18 SO
W18+1
21-0042 90-0181
18 Plastic Dip
P18+5
21-0043 —
Dice* — — —
16 TSSOP
U16+1
21-0066 90-0117
16 Narrow SO
S16+1
21-0041 90-0097
16 Wide SO
W16+1
21-0042 90-0107
16 Plastic DIP
P16+1
21-0043 —
16 Narrow SO
S16+5
21-0041 90-0097
16 SSOP
A28+2
21-0056 90-0095
28 SSOP
A28+1
21-0056 90-0095
28 TSSOP
U28+2
21-0066 90-0171
28 SO
W28+6
21-0042 90-0109
28 TSSOP
U28+2
21-0066 90-0171
Package Information
For the latest package outline information and land patterns
(footprints), go to www.maximintegrated.com/packages. Note
that a “+”, “#”, or “-” in the package code indicates RoHS status
only. Package drawings may show a different suffix character, but
the drawing pertains to the package regardless of RoHS status.
MAX3222/MAX3232/
MAX3237/MAX3241
3.0V to 5.5V, Low-Power, Up to 1Mbps,
True RS-232 Transceivers
www.maximintegrated.com Maxim Integrated
│
16
REVISION
NUMBER
REVISION
DATE DESCRIPTION PAGES
CHANGED
7 1/07 General updates 1, 15, 16, 17
8 6/18 Updated Package Information and Ordering Information 1, 15, 16, 17
Revision History
Maxim Integrated cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim Integrated product. No circuit patent licenses
are implied. Maxim Integrated reserves the right to change the circuitry and specications without notice at any time. The parametric values (min and max limits)
shown in the Electrical Characteristics table are guaranteed. Other parametric values quoted in this data sheet are provided for guidance.
Maxim Integrated and the Maxim Integrated logo are trademarks of Maxim Integrated Products, Inc.
MAX3222/MAX3232/
MAX3237/MAX3241
3.0V to 5.5V, Low-Power, Up to 1Mbps,
True RS-232 Transceivers
© 2018 Maxim Integrated Products, Inc.
│
17
For delivery, and ordering information, please visit Maxim Integrated’s online storefront at https://www.maximintegrated.com/en/storefront/storefront.html.