AN654 View Datasheet(PDF) - Maxim Integrated

Part Name

Description

Manufacturer

AN654

New RS-232 ICs Feature 1µA Supply Current, ±15kV ESD Protection, and 3V Operation

Maxim Integrated 

ESD can cause further damage to manufacturers, since equipment manufacturers may soon be barred from

selling to the European Community if their equipment fails to meet minimum levels of ESD performance,

as spelled out by IEC 801-2.

These two factors have led Maxim to develop a family of RS-232 products with ±15kV of ESD protection

(Table A). These interface ICs are the only ones to specify and achieve ±15kV ESD protection using both

the human body model and the IEC 801-2 air-gap discharge method. Maxim's high-ESD protection

eliminates the need for costly external protection devices such as TransZorbs™, while preventing

expensive field failures.

Table A. RS-232-interface ICs with ±15kV ESD Protection

Older ESD Test Methods

Two methods have been commonly used for testing the ESD susceptibility of integrated circuits. The

oldest, method 3015.7 of MIL-standard 883 (also known as the human body model), was developed to aid

manufacturers in understanding the precautions necessary for packaging and handling ICs. This method

tests each package pin against all other pins, and classifies a device according to the voltage at which the

first failure occurs (which is usually on the pin most susceptible to ESD). The applied ESD waveform is

derived from a circuit called the human body model (Figure A). The capacitance (100pF) models that of the

human body, and the resistance (1500 ) models the typical series resistance in the discharge path that

includes the body, the IC, and ground.

Figure A. Most ESD standards specify the same test circuit, but with different component values.

The other method, EIAJ Method IC-121 (also known as the machine model) applies a waveform similar to

that produced when an IC makes contact with automatic handling equipment. This method was developed

by the Electronic Industries Association of Japan (EIAJ), and also uses the setup of Figure A, but with

different values for R1 and C1. The resistance represents a human holding a metallic object such as a

screwdriver, and the capacitance is that of a human body. For the resulting waveform, rise and fall times

are steeper than those for the human body model.

The two methods are complementary, so one shouldn't be chosen over the other. Because ESD can affect

ICs during manufacturing, during pc-board assembly, and after the end product is put into service, a test

should be based on both methods to provide adequate assurance of the IC's tolerance for the rigors of

manufacturing and insertion.

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