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9

±15kV ESD-Protected, +5V RS-232 Transceivers

V+

MAX2_ _E

0.1

0.1

T_

R_

0.1

C1+

C1-

C2+

C2-

T_OUT

R_OUT

EN (EN)

SHDN (SHDN)

400k

Ω

5k

Ω

0.1

0.1

3k

Ω

+5V

R_IN

T_IN

MINIMUM SLEW-RATE TEST CIRCUIT

0V (+5V)

0V (+5V)

2500pF

V-

V+

0.1

0.1

R_

T_

0.1

C1+

C1-

C2+

C2-

T_OUT

R_OUT

EN (EN)

SHDN (SHDN)

400k

Ω

5k

Ω

0.1

0.1

7k

Ω

+5V

R_IN

T_IN

MAXIMUM SLEW-RATE TEST CIRCUIT

0V (+5V)

0V (+5V)

50pF

V-

( ) ARE FOR MAX213E

* 1

µF FOR MAX232E/MAX241E

MAX2_ _E

TRANSMITTER INPUT PULL-UP RESISTORS, ENABLE, AND SHUTDOWN ARE NOT PROVIDED ON THE MAX202E, MAX203E, AND MAX232E.

ENABLE AND SHUTDOWN ARE NOT PROVIDED ON THE MAX207E AND MAX208E.

Figure 3. Transition Slew-Rate Circuit

_______________Detailed Description

The MAX202E–MAX213E, MAX232E/MAX241E consist of

three sections: charge-pump voltage converters,

drivers (transmitters), and receivers. These E versions

provide extra protection against ESD. They survive

±15kV discharges to the RS-232 inputs and outputs,

tested using the Human Body Model. When tested

according to IEC1000-4-2, they survive ±8kV contact-

discharges and ±15kV air-gap discharges. The rugged

E versions are intended for use in harsh environments

or applications where the RS-232 connection is

frequently changed (such as notebook computers). The

standard (non-“E”) MAX202, MAX203, MAX205–

MAX208, MAX211, MAX213, MAX232, and MAX241 are

recommended for applications where cost is critical.

+5V to ±10V Dual Charge-Pump

Voltage Converter

The +5V to ±10V conversion is performed by dual

charge-pump voltage converters (Figure 4). The first

charge-pump converter uses capacitor C1 to double

the +5V into +10V, storing the +10V on the output filter

capacitor, C3. The second uses C2 to invert the +10V

into -10V, storing the -10V on the V- output filter

capacitor, C4.

a 1k

Ω pull-down resistor, and V- is internally connected

to ground by a 1k

Ω pull up resistor.

RS-232 Drivers

is ±8V when loaded with a nominal 5k

Ω RS-232

receiver. The output swing is guaranteed to meet

EIA/TIA-232E and V.28 specifications that call for ±5V

minimum output levels under worst-case conditions.

These include a 3k

maximum operating temperature. The open-circuit

output voltage swings from (V+ - 0.6V) to V-.

Input thresholds are CMOS/TTL compatible. The

unused drivers’ inputs on the MAX205E–MAX208E,

MAX211E, MAX213E, and MAX241E can be left

unconnected because 400k

are included on-chip. Since all drivers invert, the pull up

resistors force the unused drivers’ outputs low. The

MAX202E, MAX203E, and MAX232E do not have pull

up resistors on the transmitter inputs.