MAX232E datasheet(13/25 Pages) MAXIM

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MAX202E–MAX213E,

MAX232E/MAX241E

±15kV ESD-Protected,

5V RS-232 Transceivers

outputs. Therefore, after PC board assembly, the

Machine Model is less relevant to I/O ports.

Applications Information

Capacitor Selection

The capacitor type used for C1–C4 is not critical for

proper operation. The MAX202E, MAX206–MAX208E,

MAX211E, and MAX213E require 0.1µF capacitors,

and the MAX232E and MAX241E require 1µF capaci-

tors, although in all cases capacitors up to 10µF can

be used without harm. Ceramic, aluminum-electrolytic,

or tantalum capacitors are suggested for the 1µF

capacitors, and ceramic dielectrics are suggested for

the 0.1µF capacitors. When using the minimum recom-

mended capacitor values, make sure the capacitance

value does not degrade excessively as the operating

temperature varies. If in doubt, use capacitors with a

larger (e.g., 2x) nominal value. The capacitors’ effec-

tive series resistance (ESR), which usually rises at low

temperatures, influences the amount of ripple on V+

and V-.

Use larger capacitors (up to 10µF) to reduce the output

impedance at V+ and V-. This can be useful when

“stealing” power from V+ or from V-. The MAX203E and

MAX205E have internal charge-pump capacitors.

Bypass VCC to ground with at least 0.1µF. In applica-

tions sensitive to power-supply noise generated by the

charge pumps, decouple VCC to ground with a capaci-

tor the same size as (or larger than) the charge-pump

capacitors (C1–C4).

V+ and V- as Power Supplies

A small amount of power can be drawn from V+ and V-,

although this will reduce both driver output swing and

noise margins. Increasing the value of the charge-pump

capacitors (up to 10µF) helps maintain performance

when power is drawn from V+ or V-.

Driving Multiple Receivers

Each transmitter is designed to drive a single receiver.

Transmitters can be paralleled to drive multiple

receivers.

Driver Outputs when Exiting Shutdown

The driver outputs display no ringing or undesirable

transients as they come out of shutdown.

High Data Rates

These transceivers maintain the RS-232 ±5.0V mini-

mum driver output voltages at data rates of over

120kbps. For data rates above 120kbps, refer to the

Transmitter Output Voltage vs. Load Capacitance

graphs in the

Typical Operating Characteristics.

Communication at these high rates is easier if the

capacitive loads on the transmitters are small; i.e.,

short cables are best.

Table 2. Summary of EIA/TIA-232E, V.28 Specifications

PARAMETER

CONDITIONS

EIA/TIA-232E, V.28 SPECIFICA-

TIONS

0 Level

3kΩ to 7kΩ load

+5V to +15V

Data Rate

3kΩ≤ RL ≤ 7kΩ, CL ≤ 2500pF

Up to 20kbps

+3V to +15V

Instantaneous Slew Rate, Max

3kΩ≤ RL ≤ 7kΩ, CL ≤ 2500pF

30V/µs

Driver Output Short-Circuit Current, Max

100mA

Transition Rate on Driver Output

V.28

1ms or 3% of the period

Driver Output Resistance

-2V < VOUT < +2V

300Ω

EIA/TIA-232E

4% of the period

Driver Output Level, Max

No load

±25V

Driver Output Voltage

3kΩ to 7kΩ load

-5V to -15V

0 Level

1 Level

Receiver Input Level

±25V

Receiver Input Voltage

-3V to -15V

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