The MAX220–MAX249 family of line drivers/receivers is intended for all EIA/TIA-232E and V.28/V.24 communications interfaces, particularly applications where ±12V is not available. 47278

These parts are especially useful in battery-powered systems, since their low-power shutdown mode reduces power dissipation to less than 5µW. The MAX225,MAX233, MAX235, and MAX245/MAX246/MAX247 use no external components and are recommended for applications where printed circuit board space is critical.

Applications

Portable Computers

Low-Power Modems

Interface Translation

Battery-Powered RS-232 Systems

Multidrop RS-232 Networks

Features Superior to Bipolar

Operate from Single +5V Power Supply(+5V and +12V—MAX231/MAX239)

Low-Power Receive Mode in Shut down(MAX223/MAX242)

Meet All EIA/TIA-232E and V.28 Specifica

Multiple Drivers and Receivers

3-State Driver and Receiver Outputs

Open-Line Detection (MAX243)

Detailed Description

In discussing the content of RS-232C interface standards before on two points :

First, long-range communications link initially RS-232C standard data terminal equipment DTE (Data Terminal Equipment) and data communications equipment DCE (Data Communication Equipment) developed. Therefore the standards and does not consider the application of computer systems. But now it was widely borrowed for computers (more accurately, is a computer interface) between the scales of engineered with terminal or connecting standard. Clearly, some of the requirements and standards and computer systems is inconsistent, and even contradictory. With this background knowledge, we RS-232C computer incompatible with the standards of local not difficult to understand. Secondly, RS-232C criteria mentioned "sending" and "receiving" are standing DTE position, rather than standing at the position of DCE to the definition. In computer systems, often between the CPU and I/O Equipment transmission of information both DTE and therefore both sending and receiving.

RS-232C interface standards

RS-232C standards (agreement) is the full names EIA-RS-232 standards, including EIA (Electronic Industry Association), speaking on behalf of the U.S. Electronics Industry Association, Rs ( Recommeded standard), speaking on behalf of recommended standards, 232 is the identification number, the latest revision C representative RS232 (1969), in the meantime, RS232B, RS232A. . It provides connecting cables and mechanical, electrical characteristics, functions and signal transmission process. There are also common physical standard EIA�RS-232-C, EIA�RS-422-A, EIA�RS-423A, EIA�RS-485. Here only on EIA�RS-232-C (short for 232,RS232). For example, the IBM PC machines currently in the COM1, COM2 interface is RS-232C interfaces.

(1) electrical characteristics

EIA-RS-232C for electrical characteristics, functional logic of peaceful various signal lines are provided.

In the TXD and RXD :

Logic 1 (Mark) =-3V~-15V, logic 0 (space) =+3~+15V   In the RTS, CTS, DSR, DTR, and DCD control line :

Signal effective (connected, on state is voltage) =+3V~+15V, signal void (break apart, the off state, a negative voltage) =-3V~-15V

The above provisions on the criteria of logic call RS-323C Ping definition. The data (information code) : logic "1" (-) electricity ping below -3V, logic "0" (air) than the call ping +3V; for control signals; connected state (5B6) that the effective signal than +3V call ping, break apart state (off) that signals invalid call ping below -3V, When Ping is the absolute power transmission than 3V, the circuit can effectively check out somewhere between the voltage meaningless -3~+3V below or above +15V -15V the voltage believe meaningless, and therefore, the actual work should be guaranteed in the electric ping + (3~15) V between.