Exar Corporation 48720 Kato Road, Fremont CA, 94538 50-668-707 www.exar.com
SP2EH_23EH_0_060
0
ESD TOlERANCE
The
SP211EH/213EH family incorpo-
rates ruggedized ESD cells on all driver
output and receiver input pins. The ESD
structure is improved over our previous
family 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) IEC6000-4-2 Air-Discharge
c) IEC6000-4-2 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 0. This method will test the IC’s
capability to withstand an ESD transient
during normal handling such as in manu-
facturing areas where the IC's tend to be
handled frequently.
The IEC-6000-4-2, formerly IEC80-2, is
generallyusedfortestingESDonequipment
RC
Device
Under
Test
DC Power
Source
CS
RS
SW1
SW2
and systems. For system manufacturers,
they must guarantee a certain amount of
ESD protection since the system itself is ex-
posedtotheoutsideenvironmentandhuman
presence. The premise with IEC6000-4-2
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 IEC6000-4-2 is shown
on Figure . There are two methods within
IEC6000-4-2,theAirDischargemethodand
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 0. ESD Test Circuit for Human Body Model