ILX3232
ESD PROTECTION
The ILX3232 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 test
is 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
ICs 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.
Fig. 1 ESD Test Circuit for Human Body Model
The Contact Discharge Method applies the ESD current directly to the EUT. This method was devised
to reduce the unpredictability of the ESD arc. The discharge current rise time is constant since the energy is
directly transferred without the air-gap arc. In situations such as hand held systems, the ESD charge can be
directly discharged to the equipment from a person already holding the equipment. The current is transferred
on to the keypad or the serial port of the equipment directly and then travels through the PCB and finally to
the IC.
January 2009, Ver. 04
IKSEMICON [ IK SEMICON CO., LTD ]
