AN1751 - APPLICATION NOTE

5/7

V

Rg

V

Rd

Vg

Rg

Rd

IN

BR

=

×+

×

+

V

RV

Rd

V

RRd

OUT

BR

IN

IO

=

×+

×

+

/

Taking into account of:R>>Rd, Rg >> Rd and Rload >> Rd (open circuit on the test board).

With Vg = 15kV, Rg = 330

Early ageing and destruction of IC is often due to latch-up phenomena which is mainly induced by dV/dt.

Thanks to its RC structure, EMI filters provide high immunity to latch-up by integration of fast edges.

Measurements done on

figure 7 show very clearly the high efficiency of the structure.

3- Crosstalk measurements

3a - Digital crosstalk

Crosstalk phenomena are due to coupling between 2 lines (2 filters in our case). Coupling factors (

β12 and

β21) shown in figure 9 increase when distance between lines decreases, particularly in silicon dice where

distances between components are very short.

In the example above the expected signal on load RL2 is

α2 x Vg2, in fact the actual voltage at this point

has got an extra value

β21 x Vg1. This part of the Vg1 signal represents the effect of the crosstalk

phenomenon of the line 1 on the line 2.

This phenomenon has to be taken into account when drivers impose fast digital data or high frequency

analog signals. The disturbed line will be more affected if it works with low voltage signal or high load

impedance (few k

Ω).

Rg1

Vg1

αβ

1 x Vg1 + 12 x Vg2

Rg2

Vg2

αβ

2 x Vg2 + 21 x Vg1

Drivers

Receivers

Line 1

Line 2

Fig. 9: Crosstalk phemonema.