MAX232RS-232 transceiver

Connect your microcontroller’s logic to the serial world.

Manufacturer-referenced

Texas Instruments · MAX232N

PDIP-16SLLS047N · February 2024

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.

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Real View

Rendered MAX232N PDIP-16: black molded body, orientation notch and sixteen silver through-hole leads

Pinout

MAX232NPDIP-16The notch marks the top; pin 1 is at the upper left.

PCB Footprint

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Simulate the MAX232 in ProTech

MAX232: RS-232 level translator — the working circuit from our online simulator, running on this page.

1 · RunPress the green Run button in the simulator's bottom bar. The circuit solves live.
2 · Click the partWhile it runs, click the MAX232 on the sheet: its pop-up opens with live readings, dials and the datasheet.
3 · ExperimentUse the pop-up's Lab and Check pages, the oscilloscope and the voltmeters; Stop to edit any property.

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16Physical pins MAX232NPDIP-16 Manufacturer-referencedTexas Instruments

Pin diagram

Select a pin to explore its connection

Package map

Highlight

MAX232NPDIP-16The notch marks the top; pin 1 is 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

C1+

Capacitor

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.

Key specifications

The charge pump creates the positive and negative voltages RS-232 needs, using a single 5 V supply.

Nominal supply5 V

Maximum data rate120 kbit/s

Ambient range0–70 °C

Each pump capacitor1 µF

Operating profile

Supply, signals and operating conditions

MAX232 operating profile
Parameter	Value	Conditions / notes
Supply	4.5–5.5 V	5 V nominal
Inputs	TTL / CMOS · RS-232	Two drivers + two receivers
Outputs	RS-232 · TTL / CMOS	Inverting level translation
Temperature	0–70 °C	Operating ambient

Package details

MAX232N · PDIP-16

Selected package

Selected MAX232 physical package
Property	Details
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

Electrical & physical specifications

Texas Instruments MAX232N · PDIP-16 · Reference values

Manufacturer specifications 14 parameters

Scroll sideways to see all columns.

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

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.

Connections by function

Select a pin for its function, connection guidance and electrical notes.

Charge pump6 pins

RS-2324 pins

TTL / CMOS4 pins

Ground1 pin

Supply1 pin

MAX232 working principle: illustrated functional stages, basic circuit and connections — Select the diagram to read it at full resolution.

How it works

5 stages · Explore one step at a time

Step 1 / 5

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.

Step 2 / 5

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.

Step 3 / 5

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.

Step 4 / 5

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.

Step 5 / 5

Complete the connection

Power first

Pin 16 → regulated 5 V. Pin 15 → common ground. Put a 1 µF bypass close to these pins.

Regulated +5 V: VCC · pin 16
Signal ground: GND · pin 15, MCU & DB9 pin 5
C5 · 1 µF bypass: VCC ↔ GND, close to the IC

Add the charge pump

C1: 1–3. C2: 4–5. C3: 2–VCC. C4: GND–6. All are 1 µF; the + signs show polarized-capacitor orientation.

C1 · 1 µF: Pin 1 (+) ↔ pin 3 (−)
C2 · 1 µF: Pin 4 (+) ↔ pin 5 (−)
C3 · 1 µF: Pin 2 (+) ↔ VCC (−)
C4 · 1 µF: GND (+) ↔ pin 6 (−)

Connect the local UART

TX → T1IN (11). RX ← R1OUT (12). These are the logic-side connections.

MCU TX: T1IN · pin 11
R1OUT · pin 12: MCU RX

Connect the remote interface

T1OUT (14) → DB9 pin 2. DB9 pin 3 → R1IN (13). Pin 5 → common ground. This DCE female connector uses a straight-through cable to a PC’s DTE port.

T1OUT · pin 14: DB9 pin 2 · PC receive
DB9 pin 3 · PC transmit: R1IN · pin 13
DB9 pin 5: Common signal ground

Use the second channel in the same way: T2IN (10) → T2OUT (7), and R2IN (8) → R2OUT (9).

C3 may return to VCC or ground; this guide uses VCC, matching the featured circuit. Ceramic capacitors are acceptable. Follow the datasheet for the exact part and layout.

Inside MAX232

Charge pump · Line drivers · Line receivers

Functional block diagram. The charge-pump capacitors connect outside the IC; see Basic Circuit for their wiring.

Explore the circuit

Select a stage to see its role and connections

Charge pump

The first switched-capacitor stage doubles the 5 V supply. The second stage inverts that positive rail, giving the transmitters both polarities from one supply. C1 and C2 transfer charge; C3 and C4 store it. C5 keeps the supply stable.

Flying capacitors: C1: pins 1–3 · C2: pins 4–5
Reservoir capacitors: VS+: pin 2 · VS−: pin 6
External parts: Five 1 µF capacitors, including supply bypass
Driver rails: Approximately +10 V and −10 V are idealized values. Real rails and output swing drop under load.

Transmitter 1

Converts the local logic output into an inverted bipolar RS-232 signal.

InputT1IN · pin 11 · TTL / CMOS

OutputT1OUT · pin 14 · RS-232

This stage inverts the signal polarity.

Transmitter 2

A second independent transmit path, powered by the same internal charge pump.

InputT2IN · pin 10 · TTL / CMOS

OutputT2OUT · pin 7 · RS-232

This stage inverts the signal polarity.

Receiver 1

Accepts an RS-232 line signal and provides an inverted logic-level output for the local UART.

InputR1IN · pin 13 · RS-232

OutputR1OUT · pin 12 · TTL / CMOS

This stage inverts the signal polarity.

Receiver 2

The second receive path works independently of receiver 1. Both use the common ground reference.

InputR2IN · pin 8 · RS-232

OutputR2OUT · pin 9 · TTL / CMOS

This stage inverts the signal polarity.

Input resistance and reference details

The 400 kΩ pullups and 5 kΩ receiver loads show the internal equivalent in Maxim’s reference diagram. They are not extra parts you need to connect.

Selected packagePDIP-16MAX232N

Physical connections16 pinsPackage-specific numbering

Reference collection2 tables14 parameters & pin functions

Pin reference

Signal names, electrical functions and connection guidance

PDIP-16

Physical pin numbers16 pins

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MAX232 pin functions and connections
Signal	Type	Function & connection
C1+	Capacitor	Positive connection of the flying capacitor C1. Connection guidance Connect C1 (1 µF) between pins 1 and 3; positive terminal to pin 1 if polarized. Use 1 µF flying capacitors for this MAX232. Ceramic capacitors avoid polarity concerns; follow the marked +/− connections for polarized parts.
VS+	Output	Positive voltage reservoir of the internal charge pump. Connection guidance Connect the positive reservoir capacitor as shown in the manufacturer’s typical application. This is not a general-purpose supply. Positive charge-pump reservoir. Use it for the reservoir capacitor, not as an external power output.
C1−	Capacitor	Negative connection of the flying capacitor C1. Connection guidance Connect to the other side of C1 at pin 1. Use 1 µF flying capacitors for this MAX232. Ceramic capacitors avoid polarity concerns; follow the marked +/− connections for polarized parts.
C2+	Capacitor	Positive connection of the inverting capacitor C2. Connection guidance Connect C2 (1 µF) between pins 4 and 5; positive terminal to pin 4 if polarized. Use 1 µF flying capacitors for this MAX232. Ceramic capacitors avoid polarity concerns; follow the marked +/− connections for polarized parts.
C2−	Capacitor	Negative connection of the inverting capacitor C2. Connection guidance Connect to the other side of C2 at pin 4. Use 1 µF flying capacitors for this MAX232. Ceramic capacitors avoid polarity concerns; follow the marked +/− connections for polarized parts.
VS−	Output	Negative voltage reservoir of the internal charge pump. Connection guidance Connect the negative reservoir capacitor to ground; observe capacitor polarity. Not a general-purpose supply. Negative charge-pump reservoir. For a polarized reservoir capacitor, the positive terminal goes to ground.
T2OUT	Output	Channel 2 transmit output at RS-232 voltage levels. Connection guidance Connect to the remote receiver. Inverts the logic applied to T2IN (pin 10). 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.
R2IN	Input	Channel 2 receive input from an RS-232 line. Connection guidance Connect to the remote transmitter. Its converted logic appears at R2OUT (pin 9). RS-232 input only; specified input range is −30 to +30 V. The paired logic output is inverted.
R2OUT	Output	Channel 2 receive output at TTL/CMOS logic levels. Connection guidance Connect to the local UART receive input; paired with R2IN (pin 8). Logic-level output for the local UART. A negative RS-232 input produces HIGH; a positive input produces LOW.
T2IN	Input	Channel 2 transmit input from TTL/CMOS logic. Connection guidance Connect to the local UART transmit output; paired with T2OUT (pin 7). 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.
T1IN	Input	Channel 1 transmit input from TTL/CMOS logic. Connection guidance Connect to the local UART transmit output; paired with T1OUT (pin 14). 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.
R1OUT	Output	Channel 1 receive output at TTL/CMOS logic levels. Connection guidance Connect to the local UART receive input; paired with R1IN (pin 13). Logic-level output for the local UART. A negative RS-232 input produces HIGH; a positive input produces LOW.
R1IN	Input	Channel 1 receive input from an RS-232 line. Connection guidance Connect to the remote transmitter; paired with R1OUT (pin 12). RS-232 input only; specified input range is −30 to +30 V. The paired logic output is inverted.
T1OUT	Output	Channel 1 transmit output at RS-232 voltage levels. Connection guidance Connect to the remote receiver. Inverts the logic applied to T1IN (pin 11). 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.
GND	Ground	Common ground reference for logic and the transceiver. Connection guidance Connect to circuit ground and the serial connector’s signal ground. 0 V reference. Connect the local logic ground and the remote interface’s signal ground.
VCC	Supply	Positive supply input: 5 V nominal. Connection guidance Use a regulated 4.5–5.5 V supply. Place the supply bypass capacitor close to VCC and GND. 5 V nominal; keep the supply within 4.5–5.5 V. Use a common supply with the connected logic circuit.

Electrical & physical specifications

Texas Instruments MAX232N · PDIP-16 · Reference values

Manufacturer-referenced values14 parameters

Scroll within the table to see all columns and rows.

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

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 guide

Get 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 guide

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