to ±15kV without damage or latch-up. The MAX3188E/

MAX3189E’s transmitter output is characterized for pro-

tection to the following limits:

• ±15kV using the Human Body Model

• ±8kV using the Contact Discharge method specified

in IEC 1000-4-2

• ±15kV using the Air-Gap Discharge method specified

in IEC 1000-4-2

Human Body Model

Figure 2 shows the Human Body Model, and Figure 3

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,

and 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 ICs. The MAX3188E/MAX3189E enable

the design of equipment that meets the highest level

(Level 4) 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, the ESD withstand voltage measured to this

standard is generally lower than that measured using

the Human Body. Figure 4 shows the IEC 1000-4-2

model, and Figure 5 shows the current waveform for

the ±8kV IEC 1000-4-2 Level 4 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.

Power-Supply Decoupling

In most circumstances, 0.1µF bypass capacitors are

adequate for power-supply decoupling. Connect the

bypass capacitors as close to the IC as possible.

±15kV ESD-Protected, 1Mbps, 1µA

RS-232 Transmitters in SOT23-6

_______________________________________________________________________________________

5

CHARGE-CURRENT

LIMIT RESISTOR

DISCHARGE

RESISTANCE

STORAGE

CAPACITOR

Cs

100pF

1M

Ω

1500

Ω

HIGH-

VOLTAGE

DC

SOURCE

DEVICE

UNDER

TEST

Figure 2. 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 3. 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 4. IEC 1000-4-2 ESD Test Model