SP211EHEA-L/TR Просмотр технического описания (PDF) - Exar Corporation

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производитель

SP211EHEA-L/TR

High Speed +5V High Performance RS-232 Transceivers

Exar Corporation 

RC

DC Power

Source

SW1

Contact-Discharge Model

RS

RV

SW2

CS

Device

Under

Test

RS and RV add up to 330Ω for IEC61000-4-2.

Figure 11. ESD Test Circuit for IEC61000-4-2

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 situa-

tions 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.

The circuit model in Figures 10 and 11 repre-

sent 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.

For the Human Body Model, the current

limiting resistor (RS) and the source capacitor

30A

15A

0A

t=0ns

t

t=30ns

Figure 12. ESD Test Waveform for IEC61000-4-2

(CS) are 1.5kΩ an 100pF, respectively. For

IEC-61000-4-2, the current limiting resistor

(RS) and the source capacitor (CS) are 330Ω

an 150pF, respectively.

The higher CS value and lower RS value in

the IEC61000-4-2 model are more stringent

than the Human Body Model. The larger

storage capacitor injects a higher voltage

to the test point when SW2 is switched on.

The lower current limiting resistor increases

the current charge onto the test point.

Exar Corporation 48720 Kato Road, Fremont CA, 94538 • 510-668-7017 • www.exar.com

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SP211EH_213EH_101_060111

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