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MAX3222/MAX3232/
MAX3237/MAX3241*
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 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 functionally 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.
3.0V to 5.5V, Low-Power, Up to 1Mbps,
True RS-232 Transceivers
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
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
+Denotes lead-free package.
Pin Configurations
TOP VIEW
EN 1
18 SHDN
C1+ 2
Battery-Powered Equipment
Hand-Held Equipment
Peripherals
Datacom Equipment
17 VCC
V+ 3
16 GND
C1- 4
15 T1OUT
C2+ 5
Ordering Information continued at end of data sheet.
Typical Operating Circuits appear at end of data sheet.
PKG
CODE
TEMP RANGE
Applications
●●
●●
●●
●●
PINPACKAGE
PART
MAX3222
14 R1IN
C2-
6
13 R1OUT
V-
7
12 T1IN
T2OUT
8
11 T2IN
R2IN
9
10 R2OUT
DIP/SO
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 10; 5/19
MAX3222/MAX3232/
MAX3237/MAX3241
3.0V to 5.5V, Low-Power, Up to 1Mbps,
True RS-232 Transceivers
Absolute Maximum Ratings
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
Note 1: V+ and V- can have a maximum magnitude of 7V, but their absolute difference cannot exceed 13V.
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
(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
MAX3222/MAX3232/
MAX3241
0.3
1.0
MAX3237
0.5
2.0
1.0
10
µA
0.8
V
DC CHARACTERISTICS
VCC Power-Supply Current
No load, VCC = 3.3V or 5.0V,
TA = +25°C
Shutdown Supply Current
SHDN = GND, TA = +25°C
mA
LOGIC INPUTS AND RECEIVER OUTPUTS
Input Logic Threshold Low
(Note 3)
T_IN, EN, SHDN, MBAUD
Input Logic Threshold High
(Note 3)
VCC = 3.3V
2.0
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
V
VCC
- 0.1
V
RECEIVER INPUTS
Input Voltage Range
-25
Input Threshold Low
TA = +25°C
Input Threshold High
TA = +25°C
www.maximintegrated.com
25
VCC = 3.3V
0.6
1.2
VCC = 5.0V
0.8
1.5
V
V
VCC = 3.3V
1.5
2.4
VCC = 5.0V
1.8
2.4
V
Maxim Integrated │ 2
MAX3222/MAX3232/
MAX3237/MAX3241
3.0V to 5.5V, Low-Power, Up to 1Mbps,
True RS-232 Transceivers
Electrical Characteristics (continued)
(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
Input Hysteresis
Input Resistance
TYP
MAX
0.3
TA = +25°C
3
5
UNITS
V
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
Output Leakage Current
±35
VOUT = ±12V, VCC = 0V or 3V to 5.5V, transmitters
disabled
±60
mA
±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
Timing Characteristics—MAX3222/MAX3232/MAX3241
(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
120
235
MAX
UNITS
Maximum Data Rate
RL = 3kΩ, CL = 1000pF, one transmitter switching
Receiver Propagation Delay
R_IN to R_OUT, CL = 150pF
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
www.maximintegrated.com
tPHL
0.3
tPLH
0.3
kbps
μs
CL = 150pF to 1000pF
6
30
CL = 150pF to 2500pF
4
30
V/μs
Maxim Integrated │ 3
MAX3222/MAX3232/
MAX3237/MAX3241
3.0V to 5.5V, Low-Power, Up to 1Mbps,
True RS-232 Transceivers
Timing Characteristics—MAX3237
(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
Maximum Data Rate
MIN
RL = 3kΩ, CL = 1000pF, one transmitter switching,
MBAUD = GND
250
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
TYP
MAX
UNITS
kbps
tPHL
0.15
tPLH
0.15
µs
Receiver Propagation Delay
R_IN to R_OUT, CL = 150pF
Receiver Output Enable Time
Normal operation
200
ns
Receiver Output Disable Time
Normal operation
200
ns
| tPHL - tPLH |, MBAUD = GND
100
ns
| tPHL - tPLH |, MBAUD = VCC
25
ns
| tPHL - tPLH |
50
ns
Transmitter Skew
Receiver Skew
CL = 150pF
to 1000pF
VCC = 3.3V, RL = 3Ω to 7kΩ,
+3V to -3V or -3V to +3V,
TA = +25°C
Transition-Region Slew Rate
MBAUD =
GND
6
30
MBAUD =
VCC
24
150
4
30
CL = 150pF to 2500pF,
MBAUD = GND
V/μs
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.
Typical Operating Characteristics
(VCC = +3.3V, 235kbps data rate, 0.1μF capacitors, all transmitters loaded with 3kΩ, TA = +25°C, unless otherwise noted.)
MAX3222/MAX3232
SLEW RATE
vs. LOAD CAPACITANCE
22
FOR DATA RATES UP TO 235kbps
20
40
35
2
1
0
-1
-2
-3
SUPPLY CURRENT (mA)
18
16
14
-SLEW
12
10
+SLEW
8
6
-4
4
VOUT-
-5
0
0
1000
2000
3000
4000
LOAD CAPACITANCE (pF)
www.maximintegrated.com
5000
235kbps
30
25
120kbps
20
15
20kbps
10
5
2
-6
MAX3222-03
4
3
MAX3222/MAX3232
SUPPLY CURRENT vs. LOAD CAPACITANCE
WHEN TRANSMITTING DATA
MAX3222-02
VOUT+
MAX3222-01
6
5
SLEW RATE (V/µs)
TRANSMITTER OUTPUT VOLTAGE (V)
MAX3222/MAX3232
TRANSMITTER OUTPUT VOLTAGE
vs. LOAD CAPACITANCE
0
150
1000
2000
3000
4000
LOAD CAPACITANCE (pF)
5000
0
1000
2000
3000
4000
5000
LOAD CAPACITANCE (pF)
Maxim Integrated │ 4
MAX3222/MAX3232/
MAX3237/MAX3241
3.0V to 5.5V, Low-Power, Up to 1Mbps,
True RS-232 Transceivers
Typical Operating Characteristics (continued)
(VCC = +3.3V, 235kbps data rate, 0.1μF capacitors, all transmitters loaded with 3kΩ, TA = +25°C, unless otherwise noted.)
MAX3241
SLEW RATE
vs. LOAD CAPACITANCE
5.0
24
22
1 TRANSMITTER AT 235kbps
2 TRANSMITTERS AT 30kbps
0
-2.5
VOUT-
-5.0
0
1000
2000
3000
4000
14
12
+SLEW
10
30
120kbps
25
20
20kbps
15
8
10
6
5
5000
0
1000
0
2000
3000
4000
0
5000
1000
2000
3000
4000
5000
LOAD CAPACITANCE (pF)
LOAD CAPACITANCE (pF)
LOAD CAPACITANCE (pF)
MAX3237
TRANSMITTER OUTPUT VOLTAGE
vs. LOAD CAPACITANCE (MBAUD = GND)
MAX3237
TRANSMITTER OUTPUT VOLTAGE
vs. LOAD CAPACITANCE (MBAUD = VCC)
MAX3237
SLEW RATE vs. LOAD CAPACITANCE
(MBAUD = GND)
0
-2.5
-5.0
-7.5
2.5
1 TRANSMITTER AT FULL DATA RATE
4 TRANSMITTERS AT 1/16 DATA RATE
3kΩ + CL LOAD, EACH OUTPUT
VCC = 3.3V
0
-2.5
1000
2000
3000
4000
5000
4
1Mbps
SUPPLY CURRENT (mA)
1 TRANSMITTER AT FULL DATA RATE
4 TRANSMITTERS AT 1/16 DATA RATE
3kΩ + CL LOAD EACH OUTPUT
VCC = 3.3V
0
2000
500
1000
1500
LOAD CAPACITANCE (pF)
www.maximintegrated.com
70
2000
3000
20kbps
20
1 TRANSMITTER AT FULL DATA RATE
4 TRANSMITTERS AT 1/16 DATA RATE
3kΩ + CL LOADS
VCC = 3.3V
0
1000
2000
3000
4000
LOAD CAPACITANCE (pF)
AVERAGE; 10 PARTS
30
20
0
5000
MAX
40
30
4000
1 TRANSMITTER AT 512kbps
4 TRANSMITTERS AT 32kbps
3kΩ + CL LOADS
VCC = 3.3V
MBAUD = VCC
60
50
120kbps
40
1000
MAX3237
SKEW vs. LOAD CAPACITANCE
(tPLH - tPHL)
240kbps
10
2000
0
LOAD CAPACITANCE (pF)
MAX3222-11
50
30
0
1500
60
MAX3222-10
40
10
1000
MAX3237
SUPPLY CURRENT vs.
LOAD CAPACITANCE (MBAUD = GND)
-SLEW, 1Mbps
+SLEW, 1Mbps
-SLEW, 2Mbps
+SLEW, 2Mbps
20
500
MAX3237
SLEW RATE vs. LOAD CAPACITANCE
(MBAUD = VCC)
50
1 TRANSMITTER AT 240kbps
4 TRANSMITTERS AT 15kbps
3kΩ + CL LOADS
VCC = 3.3V
0
0
LOAD CAPACITANCE (pF)
60
MAX3222-09
6
2
LOAD CAPACITANCE (pF)
70
+SLEW
8
-7.5
0
-SLEW
1.5Mbps
2Mbps
-5.0
10
1.5Mbps
MAX3222-12
1 TRANSMITTER AT 240kbps
4 TRANSMITTERS AT 15kbps
3kΩ + CL LOADS
VCC = 3.3V
2Mbps
SLEW RATE (V/µs)
2.5
1Mbps
5.0
12
MAX3222-08
5.0
7.5
TRANSMITTER OUTPUT VOLTAGE (V)
MAX3222-07
7.5
TRANSMITTER OUTPUT VOLTAGE (V)
-SLEW
16
35
4
-7.5
SLEW RATE (V/µs)
18
235kbps
40
SUPPLY CURRENT (mA)
SLEW RATE (V/µs)
20
2.5
45
MAX3222-05
VOUT+
MAX3222-04
TRANSMITTER OUTPUT VOLTAGE (V)
7.5
MAX3241
SUPPLY CURRENT vs. LOAD
CAPACITANCE WHEN TRANSMITTING DATA
MAX3222-06
MAX3241
TRANSMITTER OUTPUT VOLTAGE
vs. LOAD CAPACITANCE
10
MIN
0
5000
0
500
1000
1500
2000
2500
LOAD CAPACITANCE (pF)
Maxim Integrated │ 5
MAX3222/MAX3232/
MAX3237/MAX3241
3.0V to 5.5V, Low-Power, Up to 1Mbps,
True RS-232 Transceivers
Pin Description
PIN
MAX3222
MAX3232
MAX3237
MAX3241
NAME
FUNCTION
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-
8, 15
8, 17
7, 14
5, 6, 7,
10, 12
9, 10, 11
T_OUT
9, 14
9, 16
8, 13
8, 9, 11
4–8
R_IN
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.
—
—
—
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.
www.maximintegrated.com
-5.5V Generated by the Charge Pump
RS-232 Transmitter Outputs
RS-232 Receiver Inputs
No Connection
Maxim Integrated │ 6
MAX3222/MAX3232/
MAX3237/MAX3241
3.0V to 5.5V, Low-Power, Up to 1Mbps,
True RS-232 Transceivers
Detailed Description
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.
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-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 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 worstcase 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 < 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.
VCC
VCC
0.1µF
0.1µF
VCC
C1+
C1
C1C2+
C2
C2-
C3
MAX3222
MAX3232
MAX3237
MAX3241
C2+
V-
C4
C2
C2-
T_ OUT
0V
5kΩ
GND
V+
C3
MAX3222
MAX3232
MAX3237
MAX3241
VC4
T_ OUT
R_ IN
R_ OUT
EN*
SHDN*
VCC
T_ IN
R_ IN
R_ OUT
VCC
C1
C1-
T_ IN
0V
C1+
V+
3kΩ
2500pF
VCC
EN*
5kΩ
SHDN*
GND
7kΩ
150pF
*MAX3222/MAX3237/MAX3241 ONLY
MINIMUM SLEW-RATE TEST CIRCUIT
MAXIMUM SLEW-RATE TEST CIRCUIT
Figure 1. Slew-Rate Test Circuits
www.maximintegrated.com
Maxim Integrated │ 7
MAX3222/MAX3232/
MAX3237/MAX3241
3.0V to 5.5V, Low-Power, Up to 1Mbps,
True RS-232 Transceivers
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 VCC is set to 0V in shutdown to
accommodate peripherals, such as UARTs (Figure 2).
VCC
PREVIOUS
RS-232
VCC
Rx
PROTECTION
DIODE
5kΩ
UART
Tx
GND
MAX3222/MAX3237/MAX3241
Shutdown Mode
SHDN = GND
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.
a) OLDER RS-232: POWERED-DOWN UART DRAWS CURRENT FROM
ACTIVE RECEIVER OUTPUT IN SHUTDOWN.
VCC
TO
µP
LOGIC
TRANSITION
DETECTOR
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.
MAX3237
MAX3241
R1OUTB
VCC
Rx
R1OUT
PROTECTION
DIODE
EN = VCC
UART
T1IN
Tx
GND
R1IN
T1OUT
SHDN = GND
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.
Figure 2. Detection of RS-232 Activity when the UART and
Interface are Shut Down; Comparison of MAX3237/MAX3241
(b) with Previous Transceivers (a).
www.maximintegrated.com
Applications Information
Capacitor Selection
5kΩ
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-.
Maxim Integrated │ 8
MAX3222/MAX3232/
MAX3237/MAX3241
3.0V to 5.5V, Low-Power, Up to 1Mbps,
True RS-232 Transceivers
Table 1. MAX3222/MAX3237/MAX3241
Shutdown and Enable Control Truth Table
Power-Supply Decoupling
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
Table 2. Required Minimum Capacitor
Values
V CC
(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
In most circumstances, a 0.1μF bypass capacitor is
adequate. In applications that are sensitive to powersupply 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 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.
T2
2V/div
T1
50µs/div
VCC = 3.3V
C1–C4 = 0.1µF
Figure 3. Transmitter Outputs when Exiting Shutdown or
Powering Up
www.maximintegrated.com
Maxim Integrated │ 9
3.0V to 5.5V, Low-Power, Up to 1Mbps,
True RS-232 Transceivers
6
5
4
3
VOUT+
VCC = 3.0V
2
1
T1
0
-1
T2
MAX3222-04
TRANSMITTER OUTPUT VOLTAGE (V)
MAX3222/MAX3232/
MAX3237/MAX3241
VOUT+
-2
-3
VCC
VOUT-
T3
VOUT-
-4
-5
-6
0
1
2
3
4
5
6
7
LOAD CURRENT PER TRANSMITTER (mA)
Figure 4a. MAX3241 Transmitter Output Voltage vs. Load Current per Transmitter
VCC = 3V
to 5.5V
28
C1
C2
C1+
0.1µF
26
VCC
V+
27
C3
24 C11 C2+
2
C214 T1IN
COMPUTER SERIAL PORT
MAX3241
V-
3
C4
T1OUT
9
13 T2IN
T2OUT
10
12 T3IN
T3OUT
11
+V
VCC
-V
21 R1OUTB
GND
20 R2OUTB
19 R1OUT
R1IN
4
18 R2OUT
5kΩ
R2IN
5
17 R3OUT
5kΩ
R3IN
6
16 R4OUT
5kΩ
R4IN
7
R5IN
8
15 R5OUT
23 EN
+V
5kΩ
MOUSE
5kΩ
GND
25
Tx
SHDN
22
Figure 4b. Mouse Driver Test Circuit
www.maximintegrated.com
Maxim Integrated │ 10
MAX3222/MAX3232/
MAX3237/MAX3241
3.0V to 5.5V, Low-Power, Up to 1Mbps,
True RS-232 Transceivers
VCC
0.1µF
V+
C3
C1C2+
C2
C2-
5V/div
T1OUT
5V/div
R1OUT
5V/div
VCC
C1+
C1
T1IN
MAX3222
MAX3232
MAX3237
MAX3241
VC4
5µs/div
VCC = 3.3V
T_ OUT
T_ IN
Figure 6. MAX3241 Loopback Test Result at 120kbps
R_ IN
R_ OUT
0V
VCC
EN*
SHDN*
5kΩ
1000pF
T1IN
5V/div
T1OUT
5V/div
R1OUT
5V/div
GND
* MAX3222/MAX3241 ONLY
Figure 5. Loopback Test Circuit
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.
2µs/div
VCC = 3.3V
Figure 7. MAX3241 Loopback Test Result at 235kbps
+5V
T_IN
0V
+5V
T_OUT = R_IN
5kΩ + 250pF
0V
-5V
+5V
R_OUT
150pF
0V
200ns/div
VCC = 3.3V
Figure 8. MAX3237 Loopback Test Result at 1000kbps
(MBAUD = VCC)
www.maximintegrated.com
Maxim Integrated │ 11
MAX3222/MAX3232/
MAX3237/MAX3241
3.0V to 5.5V, Low-Power, Up to 1Mbps,
True RS-232 Transceivers
Interconnection with 3V and 5V Logic
Table 3. Logic-Family Compatibility
with Various Supply Voltages
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.
SYSTEM
POWERSUPPLY
VOLTAGE
(V)
MAX32_ _
V CC
SUPPLY
VOLTAGE
(V)
3.3
3.3
5
5
5
3.3
COMPATIBILITY
Compatible with all CMOS
families.
Compatible with all TTL
and CMOS-logic families
Compatible with ACT and
HCT CMOS, and with TTL.
Incompatible with AC, HC,
and CD4000 CMOS.
Typical Operating Circuits
+3.3V
+3.3V
17
0.1µF
C1
0.1µF
2 C1+
4
5
C2
0.1µF
6
C1-
V+
MAX3222
C2+
V-
3
0.1µF
C4
0.1µF
0.1µF
T2OUT 8
TTL/CMOS
OUTPUTS
5kΩ
10 R2OUT
R2IN 9
V+
C2+
V-
GND
16
SHDN
6
C2-
C4
0.1µF
T1OUT 14
RS-232
OUTPUTS
T2OUT 7
R1IN 13
12 R1OUT
TTL/CMOS
OUTPUTS
5kΩ
9 R2OUT
R2IN 8
5kΩ
EN
C3*
0.1µF
MAX3232
10 T2IN
RS-232
INPUTS
2
TTL/CMOS
INPUTS
R1IN 14
13 R1OUT
5
C1-
VCC
11 T1IN
RS-232
OUTPUTS
11 T2IN
3
4
T1OUT 15
TTL/CMOS
INPUTS
1
1 C1+
C3*
0.1µF
7
C2-
12 T1IN
16
0.1µF
VCC
RS-232
INPUTS
5kΩ
18
GND
15
PIN NUMBERS REFER TO DIP/SO PACKAGES.
* C3 CAN BE RETURNED TO EITHER VCC OR GROUND.
* C3 CAN BE RETURNED TO EITHER VCC OR GROUND.
SEE TABLE 2 FOR CAPACITOR SELECTION
www.maximintegrated.com
Maxim Integrated │ 12
MAX3222/MAX3232/
MAX3237/MAX3241
3.0V to 5.5V, Low-Power, Up to 1Mbps,
True RS-232 Transceivers
Typical Operating Circuits (continued)
0.1µF
+3.3V
26
0.1µF
28 C1+
3
C2+
27
0.1µF
MAX3237
V-
4
23 T2IN
22 T3IN
19 T4IN
T1
T2
T3
0.1µF
T4
T1OUT 5
T2OUT 6
T3OUT 7
28 C1+
TTL/CMOS
INPUTS
RS-232
OUTPUTS
VCC
V+
2
C2+
MAX3241
T5
14 T1IN
T1OUT 9
13 T2IN
T2OUT 10
12 T3IN
T3OUT 11
RS-232
OUTPUTS
21 R1OUTB
19 R1OUT
R1IN 4
5kΩ
R2IN
18 R2OUT
5
R1IN 8
R1
TTL/CMOS
OUTPUTS
R2IN
R2
9
R3IN 11
R3
RS-232
INPUTS
5kΩ
17 R3OUT
R3IN 6
16 R4OUT
R4IN 7
5kΩ
15 R5OUT
MBAUD
13 EN
GND
SHDN
RS-232
INPUTS
5kΩ
5kΩ
R5IN 8
15
14
2
* C3 CAN BE RETURNED TO EITHER VCC OR GROUND.
www.maximintegrated.com
C4
0.1µF
T5OUT 12
5kΩ
18 R3OUT
3
T4OUT 10
5kΩ
20 R2OUT
V-
C2-
16 R1OUTB
LOGIC
OUTPUTS
C3*
0.1µF
20 R2OUTB
17 T5IN
21 R1OUT
27
24 C11
0.1µF
C2-
24 T1IN
LOGIC
INPUTS
V+
25 C11
0.1µF
VCC
26
0.1µF
0.1µF
5kΩ
23 EN
GND
SHDN
22
25
* C3 CAN BE RETURNED TO EITHER VCC OR GROUND.
Maxim Integrated │ 13
MAX3222/MAX3232/
MAX3237/MAX3241
3.0V to 5.5V, Low-Power, Up to 1Mbps,
True RS-232 Transceivers
Pin Configurations (continued)
TOP VIEW
EN
1
20 SHDN
C1+
2
19 VCC
C1+ 1
V+
3
18 GND
V+ 2
15 GND
C1-
4
17 T1OUT
C1- 3
14 T1OUT
C2+
5
16 R1IN
C2+ 4
C2-
6
15 R1OUT
C2- 5
V-
7
14 N.C.
V- 6
11 T1IN
T2OUT
8
13 T1IN
T2OUT 7
10 T2IN
R2IN
9
12 T2IN
R2IN 8
R2OUT 10
11 N.C.
MAX3222
+
16 VCC
MAX3232
13 R1IN
12 R1OUT
9 R2OUT
DIP/SO/SSOP/TSSOP
SSOP/TSSOP
C2+ 1
+
28 C1+
C2+
1
+
28 C1+
27 V+
C2-
2
27 V+
C2-
3
26 VCC
V-
3
26 VCC
V-
4
25 C1-
R1IN
4
25 GND
24 T1IN
R2IN
5
24 C1-
23 T2IN
R3IN
6
22 T3IN
R4IN
7
22 SHDN
R1IN 8
21 R1OUT
R5IN
8
21 R1OUTB
R2IN 9
20 R2OUT
T1OUT
9
20 R2OUTB
19 T4IN
T2OUT 10
19 R1OUT
18 R3OUT
T3OUT 11
18 R2OUT
17 T5IN
T3IN 12
17 R3OUT
16 R1OUTB
T2IN 13
16 R4OUT
15 MBAUD
T1IN 14
15 R5OUT
GND 2
T1OUT 5
T2OUT 6
MAX3237
T3OUT 7
T4OUT 10
R3IN 11
T5OUT 12
EN 13
SHDN 14
SSOP
www.maximintegrated.com
MAX3241
23 EN
SO/SSOP/TSSOP
Maxim Integrated │ 14
MAX3222/MAX3232/
MAX3237/MAX3241
3.0V to 5.5V, Low-Power, Up to 1Mbps,
True RS-232 Transceivers
Ordering Information (continued)
PART
TEMP RANGE
PINPACKAGE
PKG
CODE
PART
TEMP RANGE
PINPACKAGE
PKG
CODE
MAX3222EUP+
-40°C to +85°C
20 TSSOP
U20+2
MAX3232EWE+
-40°C to +85°C
16 Wide SO
W16+1
MAX3222EAP+
-40°C to +85°C
20 SSOP
A20+1
MAX3232EPE+
-40°C to +85°C
16 Plastic DIP
P16+1
MAX3222EWN+
-40°C to +85°C
18 SO
W18+1
MAX3237CAI+
0°C to +70°C
16 SSOP
A28+2
MAX3222EPN+
-40°C to +85°C
18 Plastic Dip
P18+5
MAX3237EAI+
-40°C to +85°C
28 SSOP
A28+1
—
MAX3241CUI+
0°C to +70°C
28 TSSOP
U28+2
MAX3222C/D
0°C to +70°C
Dice*
MAX3232CAE+
0°C to +70°C
16 SSOP
A16+2
MAX3241CAI+
0°C to +70°C
28 SSOP
A28+1
MAX3232CUE+
0°C to +70°C
16 TSSOP
U16+1
MAX3241CWI+
0°C to +70°C
28 SO
W28+6
MAX3232CSE+
0°C to +70°C
16 Narrow SO
S16+1
MAX3241EUI+
-40°C to +85°C
28 TSSOP
U28+2
MAX3232CWE+
0°C to +70°C
16 Wide SO
W16+1
MAX3241EAI+
-40°C to +85°C
28 SSOP
A28+1
MAX3232CPE+
0°C to +70°C
16 Plastic DIP
P16+1
MAX3241EWI+
-40°C to +85°C
28 SO
W28+6
MAX3232EUE+
-40°C to +85°C
16 TSSOP
U16+1
MAX3232ESE+
-40°C to +85°C
16 Narrow SO
S16+5
*Dice are tested at TA = +25°C, DC parameters only.
+Denotes lead-free package.
3V-Powered EIA/TIA-232 and EIA/TIA-562 Transceivers from Maxim
PART
POWERSUPPLY
VOLTAGE
(V)
NO. OF
TRANSMITTERS/
RECEIVERS
NO. OF
RECEIVERS
ACTIVE IN
SHUTDOWN
GUARANTEED
DATA
RATE
(kbps)
EIA/
TIA-232
OR 562
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
www.maximintegrated.com
FEATURES
Maxim Integrated │ 15
MAX3222/MAX3232/
MAX3237/MAX3241
3.0V to 5.5V, Low-Power, Up to 1Mbps,
True RS-232 Transceivers
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.
PACKAGE
TYPE
THERMAL RESISTANCE
(SINGLE LAYER BOARD)
THERMAL RESISTANCE
(MULTI LAYER BOARD)
PACKAGE
CODE
OUTLINE
NO.
LAND
PATTERN NO.
θJA (°C/W)
θJC (°C/W)
θJA (°C/W)
θJC (°C/W)
U20+2
21-0066
90-0116
91
20
73.8
20
20 SSOP
A20+1
21-0056
90-0094
125
33
84
32
18 SO
W18+1
21-0042
90-0181
105
22
67
23
18 Plastic Dip
P18+5
21-0043
—
90
30
NA
NA
20 TSSOP
Dice*
—
—
—
—
—
—
—
U16+1
21-0066
90-0117
106
27
90
27
16 Narrow SO
S16+1
21-0041
90-0097
115
32
75
24
16 Wide SO
W16+1
21-0042
90-0107
105
22
71
23
16 Plastic DIP
P16+1
21-0043
—
95
35
NA
NA
16 Narrow SO
S16+5
21-0041
90-0097
115
32
73
23
16 SSOP
A16+2
21-0056
90-0106
140
34
86
33
16 SSOP
A28+2
21-0056
90-0095
105
24
67
25
28 SSOP
A28+1
21-0056
90-0095
110
25
67.1
25
28 TSSOP
U28+2
21-0066
90-0171
78
13
71.6
13
28 SO
W28+6
21-0042
90-0109
80
18
59
18
28 TSSOP
U28+2
21-0066
90-0171
78
13
71.6
13
16 TSSOP
www.maximintegrated.com
Maxim Integrated │ 16
MAX3222/MAX3232/
MAX3237/MAX3241
3.0V to 5.5V, Low-Power, Up to 1Mbps,
True RS-232 Transceivers
Revision History
REVISION
NUMBER
REVISION
DATE
PAGES
CHANGED
7
1/07
General updates
1, 15, 16, 17
8
6/18
Updated Package Information and Ordering Information
1, 15, 16, 17
9
4/19
Added Thermal Resistance data in the Package Information table
16
10
5/19
Updated Package Information table
16
DESCRIPTION
For pricing, delivery, and ordering information, please visit Maxim Integrated’s online storefront at https://www.maximintegrated.com/en/storefront/storefront.html.
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 specifications 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.
© 2019 Maxim Integrated Products, Inc. │ 17
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