DocID022589 Rev 2

11/15

AN4022

Predicted results versus measured results

15

Figure 16. Gap between measured and calculated values versus current rate of rise

Figure 17. Parasitic inductance

There are three considerations regarding the first spike:



easily evaluated.



We see here the importance of the parasitic inductances especially the ground

inductance return pass. The lower the value of this inductance, the lower the value of

this transient voltage.



This spike is not the most critical for the device to protect against because I/O’s IC

circuits are dimensioned to withstand short pulses with these levels, similar to machine

model ESD tests, for example.

From Figure 14 and Figure 15 we see the predicted values for the clamping voltages at

30 ns and 60 ns are very close to the measured results, assuming the dynamic

characteristic measured in these conditions are consistent, even at high current and voltage

levels.

Note:

The study in forward polarity gives the same kind of results.

0

10

20

30

40

50

0

20

40

60

80

100

ΔV

(V)

CL

dI/dt (A/ns)

0.0

0.2

0.4

0.6

0.8

1.0

0

20

406080

100

Average value: 0.5 nH

dI/dt (A/ns)

L

(nH)

PARASITIC