Calculation of the clamping voltage

ESDA25LY

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Doc ID 16914 Rev 1

2

Calculation of the clamping voltage

2.1

Use of the dynamic resistance

The ESDA family has been designed to clamp fast spikes like ESD. Generally the PCB

dynamic resistance in addition to the classical parameters. The voltage across the

protection cell can be calculated with the following formula:

Where Ipp is the peak current through the ESDA cell.

3

Dynamic resistance measurement

The short duration of the ESD has led us to prefer a more adapted test wave, as below

defined, to the classical 8/20 µs and 10/1000 µs surges.

As the value of the dynamic resistance remains stable for a surge duration lower than 20 µs,

the 2.5 µs rectangular surge is well adapted. In addition both rise and fall times are

Figure 9.

2.5 µs duration measurement wave

2µs

t = 2.5µs

p

t

I