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

Up to 1Mbps, True RS-232 Transceivers

10

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IEC 1000-4-2

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

formance of finished equipment; it does not specifically

refer to integrated circuits. The MAX3222E/MAX3232E/

MAX3237E/MAX3241E 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.

CHARGE-CURRENT

LIMIT RESISTOR

DISCHARGE

RESISTANCE

STORAGE

CAPACITOR

Cs

100pF

1M

Ω

1500

Ω

HIGH-

VOLTAGE

DC

SOURCE

DEVICE

UNDER

TEST

Figure 4a. 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 4b. Human Body Model Current Waveform

CHARGE-CURRENT

LIMIT RESISTOR

DISCHARGE

RESISTANCE

STORAGE

CAPACITOR

Cs

150pF

50M

Ω to 100MΩ

330

Ω

HIGH-

VOLTAGE

DC

SOURCE

DEVICE

UNDER

TEST

Figure 5a. IEC 1000-4-2 ESD Test Model

tr = 0.7ns to 1ns

30ns

60ns

t

100%

90%

10%

I

Figure 5b. IEC 1000-4-2 ESD Generator Current Waveform