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CBM3232AS

OPERATION INSTRUCTION

ESD PROTECTION

The CBM3232 incorporates ruggedized ESD cells on all driver output and receiver input pins.

The ESD structure is for rugged applications and environments sensitive to electro-static

discharges and associated transients. The ESD tolerance is at least ±15kV without damage or

latch-up.

There are different methods of ESD testing applied:

a) MIL-STD-883, Method 3015.7

b) IEC1000-4-2 Air-Discharge

The Human Body Model has been the generally accepted ESD testing method for

semiconductors. This method is also specified in MIL-STD- 883, Method 3015.7 for ESD testing.

The premise of this ESD testi s to simulate the human body’s potential to store electro-static

energy and discharge it to an integrated circuit. The simulation is performed by using a test

model as shown in Figure 1. This method will test the IC’s capability to withstand an ESD

transient during normal handling such as in manufacturing areas where the IC’s tend to be

handled frequently.

The IEC-1000-4-2, formerly IEC801-2, is generally used for testing ESD on equipment and

systems. For system manufacturers, they must guarantee a certain amount of ESD protection

since the system itself is exposed to the outside environment and human presence. The premise

with IEC1000-4-2 is that the system

is required to withstand an amount of static electricity

when ESD is applied to points and surfaces of the equipment that are accessible to personnel

during normal usage. The transceiver IC receives most of the ESD current when the ESD source

is applied to the connector pins. The test circuit for IEC1000-4-2 is shown on Figure 2. There are

two methods within IEC1000-4-2, the Air Discharge method and the Contact Discharge method.

With the Air Discharge Method, an ESD voltage is applied to the equipment under test (EUT)

through air. This simulates an electrically charged person ready to connect a cable onto the rear

of the system only to find an unpleasant zap just before the person touches the back panel. The

high energy potential on the person discharges through an arcing path to the rear panel of the

system before he or she even touches the system. This energy, whether discharged directly or

through air, is predominantly a function of the discharge current rather than the discharge

voltage. Variables with an air discharge such as approach speed of the object carrying the ESD

potential to the system and humidity will tend to change the discharge current. For example, the

rise time of the discharge current varies with the approach speed.