±15kV ESD-Protected, Down to 10nA, 3.0V to 5.5V,

Up to 1Mbps, True RS-232 Transceivers

12

______________________________________________________________________________________

For the MAX3237E, all logic and RS-232 I/O pins are

characterized for protection to ±15kV per the Human

Body Model.

ESD Test Conditions

ESD performance depends on a variety of conditions.

Contact Maxim for a reliability report that documents

test setup, test methodology, and test results.

Human Body Model

Figure 4a shows the Human Body Model, and Figure

4b shows the current waveform it generates when dis-

charged into a low impedance. This model consists of

a 100pF capacitor charged to the ESD voltage of interest,

which is then discharged into the test device through a

1.5k

Ω resistor.

IEC 1000-4-2

The IEC 1000-4-2 standard covers ESD testing and

performance of finished equipment; it does not specifi-

cally refer to integrated circuits. The MAX3222E/

MAX3232E/MAX3237E/MAX3241E/MAX3246E help you

design equipment that meets level 4 (the highest level)

of IEC 1000-4-2, without the need for additional ESD-

protection components.

The major difference between tests done using the

Human Body Model and IEC 1000-4-2 is higher peak

current in IEC 1000-4-2, because series resistance is

lower in the IEC 1000-4-2 model. Hence, the ESD with-

stand voltage measured to IEC 1000-4-2 is generally

lower than that measured using the Human Body

Model. Figure 5a shows the IEC 1000-4-2 model, and

Figure 5b shows the current waveform for the ±8kV IEC

1000-4-2 level 4 ESD Contact Discharge test. The Air-

Gap Discharge test involves approaching the device

with a charged probe. The Contact Discharge method

connects the probe to the device before the probe is

energized.

Machine Model

The Machine Model for ESD tests all pins using a

200pF storage capacitor and zero discharge resis-

tance. Its objective is to emulate the stress caused by

contact that occurs with handling and assembly during

manufacturing. All pins require this protection during

manufacturing, not just RS-232 inputs and outputs.

Therefore, after PC board assembly, the Machine

Model is less relevant to I/O ports.

Table 2. Required Minimum Capacitor

Values

-6

-5

-4

-3

-2

-1

0

1

2

3

4

5

6

0

123456789

10

LOAD CURRENT PER TRANSMITTER (mA)

Figure 6a. MAX3241E Transmitter Output Voltage vs. Load

Current Per Transmitter

Table 3. Logic-Family Compatibility with

Various Supply Voltages

VCC

(V)

C1

(µF)

C2, C3, C4

(µF)

MAX3222E/MAX3232E/MAX3241E

3.0 to 3.6

0.1

0.1

4.5 to 5.5

0.047

0.33

3.0 to 5.5

0.1

0.47

MAX3237E/MAX3246E

3.0 to 3.6

0.22

0.22

3.15 to 3.6

0.1

0.1

4.5 to 5.5

0.047

0.33

3.0 to 5.5

0.22

1.0

SYSTEM

POWER-SUPPLY

VOLTAGE

(V)

VOLTAGE

(V)

COMPATIBILITY

3.3

3.3

Compatible with all

CMOS families

55

Compatible with all

TTL and CMOS

families

5

3.3

Compatible with ACT

and HCT CMOS, and

with AC, HC, or

CD4000 CMOS