The MAX232 is a dual driver/receiver that includes a capacitive voltage generator to supply TIA/EIA-232-F voltage levels from a single 5V supply. Each receiver converts TIA/EIA-232-F inputs to 5V TTL/CMOS levels. Each driver converts TTL/CMOS input levels into TIA/EIA-232-F levels. Essentially, it acts as a translator between the low-voltage world of microcontrollers (0V to 5V) and the high-voltage world of RS232 serial communication (-12V to +12V). This IC is legendary for its “charge pump” feature, which allows it to generate its own positive and negative high voltages using just four external capacitors.
MAX232 Pinout (DIP-16)
The MAX232 uses a 16-pin package. Its operation relies heavily on the external capacitors connected to the “C” pins.
| Pin | Terminal | Function |
| 1 | C1+ | Connection for Charge Pump Capacitor 1 |
| 2 | V+ | Positive Voltage Output (approx. 10V) |
| 3 | C1- | Connection for Charge Pump Capacitor 1 |
| 4 | C2+ | Connection for Charge Pump Capacitor 2 |
| 5 | C2- | Connection for Charge Pump Capacitor 2 |
| 6 | V- | Negative Voltage Output (approx. -10V) |
| 7 | T2 OUT | RS232 Line Driver Output 2 |
| 8 | R2 IN | RS232 Line Receiver Input 2 |
| 9 | R2 OUT | TTL/CMOS Receiver Output 2 |
| 10 | T2 IN | TTL/CMOS Driver Input 2 |
| 11 | T1 IN | TTL/CMOS Driver Input 1 |
| 12 | R1 OUT | TTL/CMOS Receiver Output 1 |
| 13 | R1 IN | RS232 Line Receiver Input 1 |
| 14 | T1 OUT | RS232 Line Driver Output 1 |
| 15 | GND | Ground (0V) |
| 16 | VCC | Positive Supply (5V) |
Technical Specifications
- Supply Voltage (VCC): 4.5V to 5.5V
- Input TTL Voltage: 0V to VCC
- RS232 Output Voltage Swing: ±5V to ±9V
- Data Rate: 120 kbps
- Receiver Input Resistance: 3kΩ to 7kΩ
- Propagation Delay: 0.5µs
Key Features & Benefits
- Single 5V Operation: No need for a separate +/- 12V power supply.
- Internal Charge Pump: Generates required RS232 voltages using only 4 capacitors.
- Dual Channel: Can handle both Transmit (TX) and Receive (RX) lines for two separate signals.
- Rugged Design: Built to handle the voltage swings and noise of serial cables.
Common Applications
- Serial Communication: Connecting Arduinos or PICs to a PC COM port.
- Industrial Interfacing: Talking to PLCs or CNC machines that use RS232.
- Old Hardware Mods: Reviving vintage computers or gaming consoles via serial.
- Firmware Flashing: Programming some types of routers or embedded devices.
MAX232 Equivalent & Substitutes
- ST232 (Lower power consumption variant)
- MAX3232 (3.3V compatible version for modern MCUs)
- ICL232 (Direct second-source equivalent)
- NTE1709 (Standard cross-reference)
Related Tutorials on ElxHub
- Basics: Learn more in Integrated Circuits – Basics and Working
- Pillar Guide: Learn about logic levels in our Ultimate Transistor Selection Guide
- Selection Guide: Compare interface options in our Ultimate IC Selection Guide
Conclusion
The MAX232 remains the industry standard for RS232 level shifting. While USB has replaced serial for many consumer devices, the MAX232 is still found in nearly every industrial environment where reliability over distance is key. Its clever use of charge pumps to generate high voltages from a 5V rail makes it a masterclass in efficient IC design and a must-have for any hardware hacker’s bench.
Download the IC’s Datasheet pdf
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