Introduction to the MAX3232

The MAX3232 is a dual driver/receiver that includes a capacitive voltage generator to supply RS-232 voltage levels from a single 5V supply. It is designed to interface between UART (Universal Asynchronous Receiver-Transmitter) and RS-232 serial ports, providing the necessary level shifting and signal inversion.

Key Features

• Operates from a single 5V power supply
• Requires only four external 0.1μF capacitors
• Operates up to 120 kbit/s
• Two drivers and two receivers
• ±30V input range
• Low supply current: 8mA typical
• ESD protection exceeds ±15kV using the Human Body Model (HBM)
• Upgraded version of the classic MAX232

MAX3232 Pinout and Pin Description

The MAX3232 comes in a 16-pin DIP (Dual Inline Package) or SOIC (Small Outline Integrated Circuit) package. The pinout is as follows:

Pin Number	Pin Name	Description
1	C1+	Positive terminal of capacitor C1
2	V+	Positive power supply
3	C1-	Negative terminal of capacitor C1
4	C2+	Positive terminal of capacitor C2
5	C2-	Negative terminal of capacitor C2
6	V-	Negative power supply
7	T2OUT	RS-232 driver output 2
8	R2IN	RS-232 receiver input 2
9	R2OUT	TTL/CMOS receiver output 2
10	T2IN	TTL/CMOS driver input 2
11	T1IN	TTL/CMOS driver input 1
12	R1OUT	TTL/CMOS receiver output 1
13	R1IN	RS-232 receiver input 1
14	T1OUT	RS-232 driver output 1
15	GND	Ground
16	VCC	Power supply (5V)

Functional Diagram

The functional diagram of the MAX3232 illustrates the internal structure and the signal flow within the IC.

Operating Conditions

To ensure proper operation of the MAX3232, the following operating conditions must be met:

Parameter	Min	Typ	Max	Unit
Supply Voltage (VCC)	4.5	5.0	5.5	V
Operating Temperature	-40	25	85	°C
Data Rate	–	–	120	kbps
RS-232 Input Voltage	-30	–	+30	V
RS-232 Output Voltage	±5	±8	±9	V
TTL/CMOS Input Voltage	0	–	VCC	V
TTL/CMOS Output Voltage	0	–	VCC	V

Typical Application Circuit

A typical application circuit for the MAX3232 is shown below:

In this circuit, the MAX3232 is used to interface a microcontroller’s UART with an RS-232 serial port. The four external 0.1μF capacitors (C1-C4) are used by the internal charge pump to generate the necessary RS-232 voltage levels.

Applications

The MAX3232 is widely used in various applications that require RS-232 communication, such as:

1. Industrial control systems
2. Medical equipment
3. Point-of-sale (POS) terminals
4. Telecommunications equipment
5. Computer peripherals (e.g., modems, printers)

Comparison with Other RS-232 Transceivers

The MAX3232 is one of several RS-232 transceivers available on the market. Here is a comparison of the MAX3232 with some of its alternatives:

IC	Supply Voltage	External Capacitors	Data Rate	Features
MAX3232	5V	4 x 0.1μF	120 kbps	Dual driver/receiver, ESD protection
MAX232	5V	4 x 1μF	120 kbps	Dual driver/receiver
MAX202	5V	4 x 0.1μF	120 kbps	Dual driver/receiver, low power
SP3232	3.3V	4 x 0.1μF	120 kbps	Dual driver/receiver, low voltage

While these ICs share similar functionality, the MAX3232 stands out for its use of smaller external capacitors and its enhanced ESD protection.

FAQ

1. Q: What is the difference between the MAX3232 and the MAX232?
   A: The main difference is that the MAX3232 uses smaller external capacitors (0.1μF) compared to the MAX232 (1μF). This makes the MAX3232 more suitable for space-constrained applications.

2. Q: Can the MAX3232 be used with a 3.3V microcontroller?
   A: Yes, the MAX3232 can interface with 3.3V logic levels on the TTL/CMOS side. However, the IC itself requires a 5V supply voltage.

3. Q: What is the maximum data rate supported by the MAX3232?
   A: The MAX3232 can support data rates up to 120 kbps.

4. Q: How many drivers and receivers does the MAX3232 have?
   A: The MAX3232 has two drivers and two receivers, allowing for full-duplex communication.

5. Q: What is the purpose of the external capacitors in the MAX3232 application circuit?
   A: The external capacitors are used by the internal charge pump to generate the necessary RS-232 voltage levels from the single 5V supply.

Conclusion

The MAX3232 is a versatile and reliable IC for interfacing TTL/CMOS logic with RS-232 serial communication. Its key features, such as the ability to operate from a single 5V supply, the use of small external capacitors, and enhanced ESD protection, make it a popular choice for a wide range of applications. By understanding the MAX3232 datasheet and its typical application circuit, designers can effectively integrate this IC into their projects, enabling seamless communication between digital logic and RS-232 devices.