Exar Corporation 48720 Kato Road, Fremont CA, 94538 • 50-668-707 • www.exar.com

SP207E_00_072309

RS and RV add up to 330Ω for IEC1000-4-2.

Device

Under

Test

DC Power

Source

SW1

SW2

Contact-Discharge Model

Figure 8. ESD Test Circuit for IEC000-4-2

Figure9.ESDTestWaveformforIEC1000-4-2

The Contact Discharge Method applies the

ESDcurrentdirectlytotheEUT.Thismethod

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

theequipmentfromapersonalreadyholding

the equipment. The current is transferred

on to the keypad or the serial port of the

equipment directly and then travels through

thePCBandfinallytotheIC.

ThecircuitmodelinFigures7and8represent

the typical ESD testing circuit used for all

three methods. The C

with the DC power supply when the first

switch(SW1)ison.

Now that the capacitor is charged, the sec-

ondswitch(SW2)isonwhileSW1switches

off. The voltage stored in the capacitor is

then applied through R

resistor,ontothedeviceundertest(DUT).

InESDtests,theSW2switchispulsedso

that the device under test receives a dura-

tion of voltage.

For the Human Body Model, the current

limitingresistor(R

(C

IEC-000-4-2, the current limiting resistor

(R

an 50pF, respectively.

The higher C

the IEC000-4-2 model are more stringent

than the Human Body Model. The larger

storage capacitor injects a higher voltage

tothetestpointwhenSW2isswitchedon.

The lower current limiting resistor increases

the current charge onto the test point.

t=0ns

t=30ns

0A

5A

30A

t