SP312ECT datasheet(10/15 Pages) SIPEX

10 / 15 page

Rev. 06/20/02

SP202E Series High Performance RS232 Transceivers

SP202E

HUMAN BODY

IEC1000-4-2

Family

MODEL

Air Discharge

Direct Contact

Level

Driver Outputs

±15kV

±8kV

Receiver Inputs

±15kV

±8kV

Figure 11. ESD Test Waveform for IEC1000-4-2

t=0ns

t=30ns

15A

30A

t ➙

Table 2. Transceiver ESD Tolerance Levels

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-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 models in Figures 9 and 10 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 (R

S) and the source capacitor (CS) are

1.5k

Ω an 100pF, respectively. For IEC-1000-4-

2, the current limiting resistor (R

S) and the source

capacitor (C

S) are 330Ω an 150pF, respectively.

The higher C

S value and

lower R

S 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.

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