AN2014 datasheet(18/65 Pages) STMICROELECTRONICS

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Recommendations to improve EEPROM reliability

AN2014

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DocID10701 Rev 10

Recommendations to improve EEPROM reliability

3.1

Electrostatic discharges (ESD)

ESD damage can happen any time during the product lifetime, from the moment it is

delivered to the final field service operation. ESD damage can be destructive or latent. In the

first case, a simple functional test can screen faulty devices; in the second case, the part is

partially damaged and may be able to operate correctly, but its operating life may be

drastically reduced, causing the device to fail prematurely in field service.

3.1.1

What is ESD?

Static Electricity results from the contact and separation of two bodies, which creates an

unbalance in the number of electrons at the surface of the bodies. Practically, the bodies

become charged to a specific electrical potential that depends on the material from which

they are made (see Table 2). An electrostatic discharge is defined as the transfer of charges

between two bodies at different electrical potentials. It is instantaneous (a few

nanoseconds) and thus induces high energy peaks which are very difficult to control and

predict.

3.1.2

How to prevent ESD?

An ESD can be managed if the discharge is driven through a known and controlled path on

the silicon die. Specific design rules and techniques can be used by designers to better

protect against ESDs, such as Faraday shields, perimeter ground lines or ground planes.

In a production line, the part handling until the assembly line has to be carefully ESD-

protected.

3.1.3

ST EEPROM ESD protection

ST EEPROM devices offer a specific protection circuit against Human Body Model ESDs in

accordance with AEC-Q100-002.

During write operations, the EEPROM is much more sensitive to ESDs because of the

architecture of its internal high voltage generator. Applications exposed to ESD should avoid

writing data in the EEPROM when an ESD is more likely to occur.

Table 2. ESD generation(1)

1. The charge unbalance depends on many factors such as the contact area, separation speed and relative

humidity.

ESD generation means

Static voltage levels

Walking across a carpet

1,500 V to 35,000 V

Worker on a bench

100 V to 6,000 V

Chair with urethane foam

1,500 V to 18,000 V

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