SP207ECT datasheet(10/16 Pages) SIPEX

10 / 16 page

SP207EDS/09

SP207E Series High Performance RS232 Transceivers

S and

and R

V add up to 330

add up to 330

Ω

Ω ffor IEC1000-4-2.

or IEC1000-4-2.

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

Contact-Discharge Module

SW1

SW2

Device

Under

Test

DC Power

Source

SW1

SW2

Contact-Discharge Module

Figure 8. ESD Test Circuit for IEC1000-4-2

Figure 9. ESD Test Waveform for IEC1000-4-2

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.

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-gaparc. Insituationssuchashandheldsystems,

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

andthentravelsthroughthePCBandfinallytotheIC.

The circuit model in Figures 7 and 8 represent the

typical ESD testing circuit used for all three

methods. The CS is initially charged with the DC

power supply when the first switch (SW1) is on.

Now that the capacitor is charged, the second

switch (SW2) is on while SW1 switches off. The

voltage stored in the capacitor is then applied

through RS, the current limiting resistor, onto the

device under test (DUT). In ESD tests, the SW2

switch is pulsed so that the device under test

receives a duration of voltage.

t=0ns

t=30ns

15A

30A

t ¥

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