MAX232RS-232 transceiver
Connect your microcontroller’s logic to the serial world.
MAX232 is a 16-pin serial interface IC that connects a microcontroller’s TTL/CMOS logic to an RS-232 device. Two transmitters and two receivers translate and invert the signals in both directions. It runs from a single 5 V supply; a charge pump and four external capacitors generate the driver’s positive and negative rails.
Charge pumpRS-232TTL / CMOSPower
MAX232NPDIP-16The notch marks the top; pin 1 is at the upper left.
MAX232DSOIC-16The dot identifies pin 1 at the upper left.
Click a lead or use the arrow keys. The notch marks the top; pin 1 is at the upper left.
PIN 1 · Charge pump
CapacitorC1+
Function
Positive connection of the flying capacitor C1.
How to connect
Connect C1 (1 µF) between pins 1 and 3; positive terminal to pin 1 if polarized.
Electrical note
Use 1 µF flying capacitors for this MAX232. Ceramic capacitors avoid polarity concerns; follow the marked +/− connections for polarized parts.
PIN 2 · Charge pump
OutputVS+
Function
Positive voltage reservoir of the internal charge pump.
How to connect
Connect the positive reservoir capacitor as shown in the manufacturer’s typical application. This is not a general-purpose supply.
Electrical note
Positive charge-pump reservoir. Use it for the reservoir capacitor, not as an external power output.
PIN 3 · Charge pump
CapacitorC1−
Function
Negative connection of the flying capacitor C1.
How to connect
Connect to the other side of C1 at pin 1.
Electrical note
Use 1 µF flying capacitors for this MAX232. Ceramic capacitors avoid polarity concerns; follow the marked +/− connections for polarized parts.
PIN 4 · Charge pump
CapacitorC2+
Function
Positive connection of the inverting capacitor C2.
How to connect
Connect C2 (1 µF) between pins 4 and 5; positive terminal to pin 4 if polarized.
Electrical note
Use 1 µF flying capacitors for this MAX232. Ceramic capacitors avoid polarity concerns; follow the marked +/− connections for polarized parts.
PIN 5 · Charge pump
CapacitorC2−
Function
Negative connection of the inverting capacitor C2.
How to connect
Connect to the other side of C2 at pin 4.
Electrical note
Use 1 µF flying capacitors for this MAX232. Ceramic capacitors avoid polarity concerns; follow the marked +/− connections for polarized parts.
PIN 6 · Charge pump
OutputVS−
Function
Negative voltage reservoir of the internal charge pump.
How to connect
Connect the negative reservoir capacitor to ground; observe capacitor polarity. Not a general-purpose supply.
Electrical note
Negative charge-pump reservoir. For a polarized reservoir capacitor, the positive terminal goes to ground.
PIN 7 · RS-232
OutputT2OUT
Function
Channel 2 transmit output at RS-232 voltage levels.
How to connect
Connect to the remote receiver. Inverts the logic applied to T2IN (pin 10).
Electrical note
Bipolar RS-232 output. Typical levels are about ±7 V at 5 V supply, 25 °C and a 3 kΩ load. Keep it off microcontroller GPIO inputs.
PIN 8 · RS-232
InputR2IN
Function
Channel 2 receive input from an RS-232 line.
How to connect
Connect to the remote transmitter. Its converted logic appears at R2OUT (pin 9).
Electrical note
RS-232 input only; specified input range is −30 to +30 V. The paired logic output is inverted.
PIN 9 · TTL / CMOS
OutputR2OUT
Function
Channel 2 receive output at TTL/CMOS logic levels.
How to connect
Connect to the local UART receive input; paired with R2IN (pin 8).
Electrical note
Logic-level output for the local UART. A negative RS-232 input produces HIGH; a positive input produces LOW.
PIN 10 · TTL / CMOS
InputT2IN
Function
Channel 2 transmit input from TTL/CMOS logic.
How to connect
Connect to the local UART transmit output; paired with T2OUT (pin 7).
Electrical note
LOW: 0.8 V or below. HIGH: 2 V or above. The paired RS-232 output is inverted; do not apply RS-232 voltage to this logic input.
PIN 11 · TTL / CMOS
InputT1IN
Function
Channel 1 transmit input from TTL/CMOS logic.
How to connect
Connect to the local UART transmit output; paired with T1OUT (pin 14).
Electrical note
LOW: 0.8 V or below. HIGH: 2 V or above. The paired RS-232 output is inverted; do not apply RS-232 voltage to this logic input.
PIN 12 · TTL / CMOS
OutputR1OUT
Function
Channel 1 receive output at TTL/CMOS logic levels.
How to connect
Connect to the local UART receive input; paired with R1IN (pin 13).
Electrical note
Logic-level output for the local UART. A negative RS-232 input produces HIGH; a positive input produces LOW.
PIN 13 · RS-232
InputR1IN
Function
Channel 1 receive input from an RS-232 line.
How to connect
Connect to the remote transmitter; paired with R1OUT (pin 12).
Electrical note
RS-232 input only; specified input range is −30 to +30 V. The paired logic output is inverted.
PIN 14 · RS-232
OutputT1OUT
Function
Channel 1 transmit output at RS-232 voltage levels.
How to connect
Connect to the remote receiver. Inverts the logic applied to T1IN (pin 11).
Electrical note
Bipolar RS-232 output. Typical levels are about ±7 V at 5 V supply, 25 °C and a 3 kΩ load. Keep it off microcontroller GPIO inputs.
PIN 15 · Power
GroundGND
Function
Common ground reference for logic and the transceiver.
How to connect
Connect to circuit ground and the serial connector’s signal ground.
Electrical note
0 V reference. Connect the local logic ground and the remote interface’s signal ground.
PIN 16 · Power
SupplyVCC
Function
Positive supply input: 5 V nominal.
How to connect
Use a regulated 4.5–5.5 V supply. Place the supply bypass capacitor close to VCC and GND.
Electrical note
5 V nominal; keep the supply within 4.5–5.5 V. Use a common supply with the connected logic circuit.
At a glance
RS-232 transceiver
The charge pump creates the positive and negative voltages RS-232 needs, using a single 5 V supply.
5 VNominal supply
120 kbit/sMaximum data rate
0–70 °CAmbient range
1 µFEach pump capacitor
Operating profile
MAX232N
Electrical & physical specifications
Key parameters and their test conditions
- Supply voltage
- 4.5–5.5 VConditions / notes: 5 V nominal; recommended operating range
- Maximum data rate
- 120 kbit/sConditions / notes: One transmitter output switching; see datasheet test conditions
- Transmit / receive channels
- 2 / 2Conditions / notes: Two drivers and two receivers
- Supply current
- 8 mA typ. / 10 mA max.Conditions / notes: VCC = 5.5 V, outputs open, ambient = 25 °C
- Driver output
- +7 V / −7 V typicalConditions / notes: VCC = 5 V, ambient = 25 °C, 3 kΩ load to GND; +5 V / −5 V guaranteed limits
- Logic input HIGH / LOW
- ≥ 2 V / ≤ 0.8 VConditions / notes: T1IN and T2IN; values between thresholds are undefined
Package details
Follows the selected physical package
- Manufacturer
- Texas Instruments
- Part number
- MAX232N
- Package
- PDIP-16
- Connections
- 16 pins
- Mounting
- Through-hole
- Lead pitch
- 2.54 mm
- Package code
- N
- Thermal reference
- 60.6 °C/W
Connections by function
Select a pin to open its function, electrical notes and wiring guidance.
Charge pump6 pins
RS-2324 pins
TTL / CMOS4 pins
Power2 pins
Charge pump6 pins
RS-2324 pins
TTL / CMOS4 pins
Power2 pins
1. Two electrical languages
A microcontroller’s UART uses logic levels, while an RS-232 port uses positive and negative voltages. The MAX232 translates between them. It changes voltage levels and polarity; it does not create a baud rate or decode the data.
2. Create the driver rails
Connect pin 16 to 5 V and pin 15 to ground. C1 transfers charge in the voltage doubler; C2 supports the inverter. C3 and C4 hold the positive and negative rails, and C5 bypasses the supply. This MAX232 circuit uses 1 µF for all five capacitors.
The diagram’s approximately ±10 V rails explain the unloaded charge-pump action. Actual rails and output swing depend on supply, load and losses.
3. Transmit to RS-232
Microcontroller TX feeds T1IN, pin 11. T1OUT, pin 14, drives the serial line with an inverted bipolar signal: logic HIGH becomes a negative RS-232 voltage, and logic LOW becomes positive. Channel 2 works the same way through pins 10 and 7.
4. Receive into the UART
The remote transmitter reaches R1IN, pin 13. The receiver converts the RS-232 signal into a logic output at R1OUT, pin 12, for the microcontroller’s RX input. A negative input gives logic HIGH; a positive input gives LOW. The second receiver uses pins 8 and 9.
5. Complete the connection
The Basic Circuit shows a DCE female DB9 connector from its mating face: pin 2 carries the MAX232’s output, pin 3 accepts the PC’s transmit signal, and pin 5 is signal ground. A straight-through cable joins it to a PC DTE port. TX and RX operate independently, allowing two-way communication.
Keep the two sides separate. Logic pins go to the microcontroller; RS-232 pins go to the serial port. Use a common ground, correct capacitor polarity and the datasheet for your exact part.
Select a colored stage to explore it. Capacitors are external; the shaded blocks are inside the IC.
Follow the colored wires from the MCU to the MAX232 and the serial connector. Channel 2 is unused; this is a connection guide.
Pin reference
Select a pin to explore its function and connection.
16 pins
| Pin | Signal | Type | Function |
|---|---|---|---|
| C1+ | Capacitor | Positive connection of the flying capacitor C1. | |
| VS+ | Output | Positive voltage reservoir of the internal charge pump. | |
| C1− | Capacitor | Negative connection of the flying capacitor C1. | |
| C2+ | Capacitor | Positive connection of the inverting capacitor C2. | |
| C2− | Capacitor | Negative connection of the inverting capacitor C2. | |
| VS− | Output | Negative voltage reservoir of the internal charge pump. | |
| T2OUT | Output | Channel 2 transmit output at RS-232 voltage levels. | |
| R2IN | Input | Channel 2 receive input from an RS-232 line. | |
| R2OUT | Output | Channel 2 receive output at TTL/CMOS logic levels. | |
| T2IN | Input | Channel 2 transmit input from TTL/CMOS logic. | |
| T1IN | Input | Channel 1 transmit input from TTL/CMOS logic. | |
| R1OUT | Output | Channel 1 receive output at TTL/CMOS logic levels. | |
| R1IN | Input | Channel 1 receive input from an RS-232 line. | |
| T1OUT | Output | Channel 1 transmit output at RS-232 voltage levels. | |
| GND | Ground | Common ground reference for logic and the transceiver. | |
| VCC | Supply | Positive supply input: 5 V nominal. |
No pins match. Try a signal name or choose All pins.
Electrical & physical specifications
Texas Instruments MAX232N · PDIP-16 · Reference values
Manufacturer specifications 14 parameters
| Parameter | Value | Conditions / notes |
|---|---|---|
| Supply voltage | 4.5–5.5 V | 5 V nominal; recommended operating range |
| Maximum data rate | 120 kbit/s | One transmitter output switching; see datasheet test conditions |
| Transmit / receive channels | 2 / 2 | Two drivers and two receivers |
| Supply current | 8 mA typ. / 10 mA max. | VCC = 5.5 V, outputs open, ambient = 25 °C |
| Driver output | +7 V / −7 V typical | VCC = 5 V, ambient = 25 °C, 3 kΩ load to GND; +5 V / −5 V guaranteed limits |
| Logic input HIGH / LOW | ≥ 2 V / ≤ 0.8 V | T1IN and T2IN; values between thresholds are undefined |
| Receiver input range | −30 to +30 V | R1IN and R2IN only |
| Receiver hysteresis | 0.5 V typical | At VCC = 5 V |
| Operating temperature | 0 to +70 °C | MAX232N commercial grade; MAX232I has a different range |
| Charge-pump capacitors | 4 × 1 µF | Plus supply bypass; follow the typical application, section 8 |
| Package | PDIP-16, 16 leads | TI N package; 2.54 mm lead pitch |
| Junction-to-ambient | 60.6 °C/W | PDIP-16; datasheet thermal characterization conditions |
| Supply absolute maximum | −0.3 to +6 V | Stress rating only, not an operating range |
| Maximum junction temperature | 150 °C | Absolute maximum, not the ambient operating rating |
No specifications match. Try a parameter name or a unit.
Reference: TI SLLS047N, sections 4–8 and package drawings. Check the exact manufacturer and suffix before substituting MAX232A, MAX3232 or another family member. Verify a production footprint against your ordered part.
Build a UART-to-RS-232 interface
Route UART TX to T1IN (11), then T1OUT (14) to the remote receiver. Bring the remote transmit line into R1IN (13), with R1OUT (12) returning to UART RX.
Use a common signal ground. Check the remote connector’s DTE/DCE pin assignment.
Manufacturer application guideGet the charge pump right
Use the four 1 µF pump capacitors and a local supply bypass as shown in the reference circuit. Keep these connections short and check polarity when using polarized capacitors.
VS+ and VS− serve the charge pump; they are not supply rails for other components.
Manufacturer application guideTake it into ProTech
Find MAX232 in the Components Library to place its schematic symbol and connect its pins.
Schematic available · Simulation model pendingOpen ProTech