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

IEC1000-4-2

The IEC1000-4-2 standard covers ESD testing and

performance of finished equipment; it does not

specifically refer to integrated circuits. The

MAX202E/MAX203E–MAX213E, MAX232E/MAX241E

help you design equipment that meets level 4 (the

highest level) of IEC1000-4-2, without the need for

additional ESD-protection components.

The major difference between tests done using the

Human Body Model and IEC1000-4-2 is higher peak

current in IEC1000-4-2, because series resistance is

lower in the IEC1000-4-2 model. Hence, the ESD

withstand voltage measured to IEC1000-4-2 is

generally lower than that measured using the Human

Body Model. Figure 7b shows the current waveform for

the 8kV IEC1000-4-2 level-four ESD contact-discharge

test.

The air-gap 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

resistance. Its objective is to emulate the stress caused

by contact that occurs with handling and assembly

during manufacturing. Of course, 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.

CHARGE CURRENT

LIMIT RESISTOR

DISCHARGE

RESISTANCE

STORAGE

CAPACITOR

Cs

150pF

HIGH-

VOLTAGE

DC

SOURCE

DEVICE

UNDER

TEST

Figure 7a. IEC1000-4-2 ESD Test Model

tr = 0.7ns to 1ns

30ns

60ns

t

100%

90%

10%

I

Figure 7b. IEC1000-4-2 ESD Generator Current Waveform

CHARGE-CURRENT

LIMIT RESISTOR

DISCHARGE

RESISTANCE

STORAGE

CAPACITOR

Cs

100pF

HIGH-

VOLTAGE

DC

SOURCE

DEVICE

UNDER

TEST

Figure 6a. Human Body ESD Test Model

90%

36.8%

TIME

CURRENT WAVEFORM

PEAK-TO-PEAK RINGING

(NOT DRAWN TO SCALE)

Ir

10%

0

0

AMPERES

Figure 6b. Human Body Model Current Waveform