SP3282 Datasheet, PDF(12/15 Page) Sipex Corporation – Intelligent +2.35V to +5.5V RS-232 Transceivers

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SP3282 Datasheet, PDF (12/15 Pages) Sipex Corporation – Intelligent +2.35V to +5.5V RS-232 Transceivers

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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 situations 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 18 and 19 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.

For the Human Body Model, the current limiting

resistor (RS) and the source capacitor (CS) are

1.5kâ¦ an 100pF, respectively. For IEC-1000-4-2,

the current limiting resistor (RS) and the source

capacitor (CS) are 330â¦ an 150pF, respectively.

RCC

DC Power

Source

SW1

The higher C value and lower R value in the

IEC1000-4-2 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.

30A

15A

t=0ns

t=30ns

tâ

Figure 20. ESD Test Waveform for IEC1000-4-2

RSS

CSS

SW2

Device

Under

Test

Figure 18. ESD Test Circuit for Human Body Model

RCC

DC Power

Source

SW1

Contact-Discharge Module

RRSS

SW2

Device

CSS

Under

Test

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

Figure 19. ESD Test Circuit for IEC1000-4-2

Date: 02/24/05

SP3282EB Intelligent +2.35V to +5.5V RS-232 Transceivers

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