MAX232

The MAX232 is an integrated circuit by Maxim Integrated Products, now a subsidiary of Analog Devices, that converts signals from a TIA-232 (RS-232) serial port to signals suitable for use in TTL-compatible digital logic circuits.

[1] The drivers provide TIA-232 voltage level outputs (about ±7.5 volts) from a single 5-volt supply by on-chip charge pumps and external capacitors.

[1] The MAX232 replaced an older pair of chips MC1488 and MC1489 that performed similar RS-232 translation.

Usually, these signals can be omitted when, for example, communicating with a PC's serial interface, or when special cables render them unnecessary.

A notable addition is the MAX316x which is able to be electrically reconfigured between differential 5 V (RS-422 and RS-485) and single-ended RS-232 albeit at reduced voltage.

MAX232 chip in DIP-16 package
The die of a MAX232
MAX232 pinout: Red: power, Yellow: charge pump capacitors,
Blue: outputs, Green: inputs,
Pins 9–12: TTL/CMOS I/O voltages
TIA-232 to TTL converters that use MAX232