ICL3221EM, ICL3221EF

5. ±15kV ESD Protection

FN7552 Rev.2.00

Page 18 of 22

May.29.19

5.

±15kV ESD Protection

All pins on the ICL3221EM and ICL3221EF devices include ESD protection structures, but the families

incorporate advanced structures that allow the RS-232 pins (transmitter outputs and receiver inputs) to survive

ESD events up to ±15kV. The RS-232 pins are particularly vulnerable to ESD damage because they typically

connect to an exposed port on the exterior of the finished product. Touching the port pins or connecting a cable

can cause an ESD event that might destroy unprotected ICs. The ESD structures protect the device whether or

not it is powered up, protect without allowing any latch-up mechanism to activate, and do not interfere with

RS-232 signals as large as ±25V.

5.1

Human Body Model (HBM) Testing

The Human Body Model (HBM) test method emulates the ESD event delivered to an IC during human handling.

The tester delivers the charge through a 1.5kΩ current limiting resistor so the test is less severe than the

IEC61000 test, which uses a 330Ω limiting resistor. The HBM method determines an IC’s ability to withstand the

ESD transients typically present during handling and manufacturing. Due to the random nature of these events,

each pin is tested with respect to all other pins. The RS-232 pins on “E” family devices can withstand HBM ESD

events to ±15kV.

5.2

IEC61000-4-2 Testing

The IEC61000 test method applies to finished equipment, rather than to an individual IC. Therefore, the pins most

likely to suffer an ESD event are those that are exposed to the outside world (the RS-232 pins in this case), and

the IC is tested in its typical application configuration (power applied) rather than testing each pin-to-pin

combination. The lower current limiting resistor coupled with the larger charge storage capacitor yields a test that

is much more severe than the HBM test. The extra ESD protection built into this device’s RS-232 pins allows the

design of equipment meeting Level 4 criteria without the need for additional board level protection on the RS-232

port.

5.3

Air-Gap Discharge Test Method

For the air-gap discharge test method, a charged probe tip moves toward the IC pin until the voltage arcs to it.

The current waveform delivered to the IC pin depends on factors such as approach speed, humidity, and

temperature, so it is difficult to obtain repeatable results. The “E” device RS-232 pins withstand ±15kV air-gap

discharges.

5.4

Contact Discharge Test Method

During the contact discharge test, the probe contacts the tested pin before the probe tip is energized, and

eliminate the variables associated with the air-gap discharge. The result is a more repeatable and predictable

test, but equipment limits prevent testing devices at voltages higher than ±8kV. All “E” family devices survive ±8kV

contact discharges on the RS-232 pins.