3.0V, ±15kV ESD-Protected RS-232

Transceiver for PDAs and Cell Phones

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7

Unlike other RS-232 interface devices where the receiver

for the receiver outputs and sets thresholds for the

receiver inputs. This feature allows a great deal of flexi-

bility in interfacing to many different types of systems

with different logic levels. Connect this input to the host

logic supply (1.8V

PDA/Cell-Phone Application section.

±15kV ESD Protection

As with all Maxim devices, ESD-protection structures are

incorporated on all pins to protect against electrostatic

discharges (ESDs) encountered during handling and

assembly. The MAX3386E’s driver outputs and receiver

inputs have extra protection against static electricity.

Maxim has developed state-of-the-art structures to pro-

tect these pins against an ESD of ±15kV without damage.

The ESD structures withstand high ESD in all states: nor-

mal operation, shutdown, and powered down. After an

ESD event, Maxim’s “E” version devices keep working

without latchup, whereas competing RS-232 products

can latch and must be powered down to remove latchup.

ESD protection can be tested in various ways. The trans-

mitter outputs and receiver inputs of this product family

are characterized for protection to the following limits:

1) ±15kV using the Human Body Model

2) ±8kV using the Contact Discharge method specified

in IEC 1000-4-2

3) ±15kV using IEC 1000-4-2’s Air-Gap Discharge

method

ESD Test Conditions

ESD performance depends on a variety of conditions.

Contact Maxim for a reliability report that documents

test setup, methodology, and results.

Human Body Model

Figure 3a shows the Human Body Model, and Figure 3b

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 ICs. The MAX3386E helps 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 4a shows the IEC 1000-4-2 model, and

Figure 4b 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.

CHARGE-CURRENT

LIMIT RESISTOR

DISCHARGE

RESISTANCE

STORAGE

CAPACITOR

Cs

100pF

1M

1500

Ω

HIGH-

VOLTAGE

DC

SOURCE

DEVICE

UNDER

TEST

Figure 3a. 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 3b. Human Body Current Waveform