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

SP207E_00_072309

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ESD TOLERANCE

The SP207E Family incorporates rug-

gedized ESD cells on all driver output

and receiver input pins. The ESD struc-

ture is improved over our previous fam-

ily for more rugged applications and

environments sensitive to electro-static

discharges and associated transients. The

improved ESD tolerance is at least +5kV

without damage nor latch-up.

There are different methods of ESD testing

applied:

a) MIL-STD-883, Method 305.7

b) IEC000-4-2 Air-Discharge

c) IEC000-4-2 Direct Contact

The Human Body Model has been the

generally accepted ESD testing method

for semiconductors. This method is also

specifiedinMIL-STD-883,Method3015.7

for ESD testing. The premise of this ESD

testisto simulate the human body’spotential

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 7. This method will test the IC’s

capability to withstand an ESD transient

during normal handling such as in manu-

facturing areas where the ICs tend to be

handled frequently.

The IEC-000-4-2, formerly IEC80-2, is

generallyusedfortestingESDonequipment

and systems. For system manufacturers,

Device

Under

Test

DC Power

Source

SW1

SW2

theymustguaranteeacertainamountofESD

protection since the system itself is exposed

to the outside environment and human pres-

ence. The premise with IEC000-4-2 is that

thesystemisrequiredtowithstandanamount

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 IEC000-4-2 is shown on Figure 8.

There are two methods within IEC000-4-2,

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)throughair.Thissimulatesan

electrically charged person ready to connect

a cable onto the rear of the system only to

findanunpleasantzapjustbeforetheperson

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

throughair,ispredominantlyafunctionofthe

discharge current rather than the discharge

voltage. Variableswithanairdischargesuch

asapproachspeedoftheobjectcarryingthe

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.

Figure 7. ESD Test Circuit for Human Body Model