MAX3232 Line Receiver: Pinout, Datasheet, Applications with Circuit

MAX3232 IC is extensively used for serial communication in between Microcontroller and a computer for changing the TTL/CMOS logic levels to RS232. It consists of two line drivers, two line receivers, and a dual charge-pump circuit with ±15-kV ESD protection terminal to terminal (serial-port connection terminals, including GND). The device meets the requirements of TIA/EIA-232-F and provides the electrical interface between an asynchronous communication controller and the serial-port connector. The charge pump and four small external capacitors allow operation from a single 3-V to 5.5-V supply. The devices operate at data signaling rates up to 250 kbit/s and a maximum of 30-V/μs driver output slew rate.

MAX3232 Line Receiver and Driver

MAX3232 Simplified Schematic

Figure 1: MAX3232 Simplified Schematic

Specifications

Pinout and Functions

Figure 2: MAX3232 Pin Configuration

Table 1: Pin Functions

Applications

Using Examples

1) Standard Application

The following figure is a standard working circuit of the chip. The circuit can be designed based on the above pin configuration:

Figure 3: MAX3232 Standard Application

(2) Connect with STM32

Any serial port of the STM32 chip is connected to 232_RX and 232_TX in the figure above, and RS232_TXD and RS232_RXD in the figure below are connected to a 9-pin serial port hardware.

Figure 4: MAX3232 Connect with STM32

(3) RS232 set to TTL2 serial port module

Figure 5: RS232 to TTL2 Serial Port Module

* DB-9 Pinout

1) DCD (Data Carrier Detect): Carrier detection. It is mainly used by the Modem to notify the computer that it is online, that is, the Modem detects the dial tone and is online.

2) RXD (Receive Data): This pin is used to receive data from external devices. When you use the Modem, you will find that the RXD indicator light is flashing, indicating that there is data entering the RXD pin.

3) TXD (Transmit Data): This pin sends the computer's data to the external device. When you use the Modem, you will find the TXD indicator light flashing, indicating that the computer is sending data through the TXD pin.

4) DTR (Data Terminal Ready): The data terminal is ready. When this pin is high, it notifies the Modem that data transmission can be carried out and the computer is ready.

5) GND (Ground): logical ground.

6) DSR (Data Set Ready): When this pin is high, it notifies the computer that the Modem is ready for data communication.

7) RTS (Request To Send): It is controlled by the computer to notify the Modem to send data to the computer immediately; otherwise, the Modem will temporarily put the received data into the buffer.

8) CTS (Clear to Send): It is controlled by the Modem to notify the computer to send the data to be transmitted to the Modem.

9) RI (Ring Indicator): Modem notifies the computer that a call is coming in, and the computer decides whether to answer the call.

To achieve communication between serial ports, at least three pins are needed, namely: RXD, TXD, GND. RXD is connected to other serial port lines TXD, while TXD is connected to RXD, and GND is connected to GND. This realizes communication between serial ports. The communication is full-duplex, that is, data can be sent/received at the same time. Although it is serial, full-duplex can be achieved because the sending/receiving does not use one channel.

Figure 6: RS232 to TTL2 Serial Port Module Schematic Diagram

MAX3232 vs MAX232

1. MAX232 is powered by 5V voltage, while MAX3232 is powered by 5V or 3.3V.

2. MAX232 has a large power consumption, and consumes 5mA when the supply voltage is 5V. While MAX3232 has a small power consumption, and consumes 0.3mA when the supply voltage is 5V or 3.3V.

3. MAX232 connects to four external 1uF capacitors, while MAX3232 connects to four external 0.1uF (104) capacitors.

4. MAX232 is generally for civilian use, while MAX3232 is generally for military use.

5. There is a difference in price.