MAX 232
INTRODUCTION
The MAX 232 contain four sections:
dual charge- pump DC-DC voltage converters,
RS-232 drivers, RS-232 receivers, and receiver and transmitter enable
control inputs.
MAX 232
The MAX232 from Maxim was the first IC which in one
package contains the necessary drivers (two) and receivers (also two), to adapt
the RS-232 signal voltage levels to TTL logic. It became popular, because it
just needs one voltage (+5V) and generates the necessary RS-232 voltage levels
(approx. -10V and +10V) internally. This greatly simplified the design of
circuitry. Circuitry designers no longer need to design and build a power
supply with three voltages (e.g. -12V, +5V, and +12V), but could just provide
one +5V power supply, e.g. with the help of a simple 78x05 voltage converter.
The MAX232 has a successor, the MAX232A.
The ICs are almost identical, however, the MAX232A is much more often used (and
easier to get) than the original MAX232, and the MAX232A only needs external
capacitors 1/10th the capacity of what the original MAX232 needs.
It should be noted that the MAX232
is just a driver/receiver. It does not generate the necessary RS-232 sequence
of marks and spaces with the right timing, it does not decode the RS-232
signal, and it does not provide a serial/parallel conversion. All it does is to convert signal voltage
levels. Generating serial data with the right timing and decoding serial
data has to be done by additional circuitry, e.g. by a 16550 UART or one of these small micro
controllers (e.g. Atmel AVR, Microchip PIC) getting more and more popular.
APPLICATIONS
1. Portable
computers
2.
Low power Modems
3.
Interface translation
4. Battery
powered RS-232 systems
CONCLUSION
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