Technical information

DALC208

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Technical information

2.1

Surge protection

The DALC208SC6 is particularly optimized to perform surge protection based on the rail to

rail topology.

The clamping voltage V

V

V

with

V

(V

According to the curve Figure 7 we assume that the value of the dynamic resistance of the

clamping diode is typically R

Ω and V

For an IEC 61000-4-2 surge Level 4 (Contact Discharge: V

Ω), V

V

′ 24 A.

So, we find:

–V

′ +23V

–V

′ -18V

Note:

The calculations do not take into account phenomena due to parasitic inductances.

2.2

Surge protection application example

If we consider that the connections from the pin REF

done by two tracks of 10 mm long and 0.5 mm large; we assume that the parasitic

inductances of these tracks are about 6 nH. So when an IEC 61000-4-2 surge occurs, due

to the rise time of this spike (tr = 1 ns), the voltage V

The dI/dt is calculated as: dI/dt = Ip/tr

′ 24 A/ns

The overvoltage due to the parasitic inductances is: Lw.dI/dt = 6 x 24

′ 144V

By taking into account the effect of these parasitic inductances due to unsuitable layout, the

clamping voltage will be :

–V

′ 167V

–V

′ -162V

We can reduce as much as possible these phenomena with simple layout optimization.

It’s the reason why some recommendations have to be followed (See Section 2.3: How to

ensure good ESD protection).