SP3220EB datasheet(14/19 Pages) SIPEX

14 / 19 page

Rev: A Date:12/11/03

SP3220EB/EU +3.0 to +5.0V RS-232 Transceivers

SW1

SW2

Device

Under

Test

DC Power

Source

SW1

SW2

Figure 20. ESD Test Circuit for Human Body Model

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 transfered

without the air-gap arc. In situations such as

hand held systems, the ESD charge can be

directly discharged to the equipment from a

person directly discharged to 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 models in Figure 20 and 21 repre-

sent the typical ESD testing circuits used for all

three methods. The C

S 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 R

S, the current limiting

resistor, onto the device under test (DUT). In

ESD tests, the SW2 switch is pulsed so that the

device under test recives a duration of voltage.

Figure 21. ESD Test Circuit for 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

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