Human Body Model

Figure 2a shows the Human Body Model, and Figure

2b 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 inter-

est, which is then discharged into the device through a

1.5k

Ω resistor.

IEC1000-4-2

The IEC1000-4-2 standard covers ESD testing and per-

formance of finished equipment; it does not specifically

refer to integrated circuits. The MAX1406 helps you

design equipment that meets Level 4 (the highest level)

of IEC1000-4-2, without additional ESD-protection com-

ponents.

The main difference between tests done using the

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

current in IEC1000-4-2 (Figure 3). Because series resis-

tance is lower in the IEC1000-4-2 ESD test model, the

ESD withstand voltage measured to this standard is

generally lower than that measured using the Human

Body Model. Figure 3b shows the current waveform for

the ±8kV IEC1000-4-2 Level 4 ESD Contact-Discharge

test.

The Air-Gap test involves approaching the device with

a charge probe. The Contact-Discharge method con-

nects the probe to the device before the probe is ener-

gized.

Machine Model

The Machine Model for ESD testing uses a 200pF stor-

age capacitor and zero-discharge resistance. It mimics

the stress caused by handling during manufacturing

and assembly. Of course, all pins (not just RS-232

inputs and outputs) require this protection during man-

ufacturing. Therefore, the Machine Model is less rele-

vant to the I/O ports than are the Human Body Model

and IEC1000-4-2.

±15kV ESD-Protected, EMC-Compliant,

230kbps, 3-Tx/3-Rx RS-232 IC

6

_______________________________________________________________________________________

Figure 2. Human Body ESD Test Model and ESD-Generator

Current Waveform

Figure 3. IEC1000-4-2 Test Model and ESD-Generator Current

Waveform

90%

36.8%

TIME

CURRENT WAVEFORM

PEAK-TO-PEAK RINGING

(NOT DRAWN TO SCALE)

Ir

10%

0

0

AMPERES

30ns

60ns

t

100%

90%

10%

I

CHARGE-CURRENT

LIMIT RESISTOR

DISCHARGE

RESISTANCE

STORAGE

CAPACITOR

Cs

100pF

HIGH-

VOLTAGE

DC

SOURCE

DEVICE

UNDER

TEST

CHARGE-CURRENT

LIMIT RESISTOR

DISCHARGE

RESISTANCE

STORAGE

CAPACITOR

Cs

150pF

HIGH-

VOLTAGE

DC

SOURCE

DEVICE

UNDER

TEST

a)

a)

b)

b)