Predicted results versus measured results

AN4022

10/15

DocID022589 Rev 2

Figure 14. Measurements and predicted values for 30 ns clamping value

Figure 15. Measurements and predicted values for 60 ns clamping value

Figure 13 shows the predicted results for the first spike voltage are far from the measured

values. In fact, the dl/dt during the first spike is very high, between 10 A/ns up to 80 A/ns

(the current rise time is around 0.75 ns). If we represent the

V between the measured and

the calculated

values versus the dl/dt, we get the curve in Figure 16. From this curve,

we can extract the value, shown in Figure 17. This value is near a constant, equal to the

parasitic inductance of the measurement loop (board, ground etc), in this case around

0.5 nH.

V

CL

(V)

0

2

4

6

8

10

12

14

16

18

20

0

2

4

6

8

101214

16

Predicted 30 ns Min

Predicted 30 ns Typ

Predicted 30ns Max

Measured 30 ns

Breakdown

V

PP

(KV)

0

2

4

6

8

10

12

14

16

18

20

02

46

8

10

12

14

16

Predicted 60 ns Min

Predicted 60 ns Typ

Predicted 60ns Max

Measured 60 ns

Breakdown

V

PP

(KV)

V

CL

(V)

V

dl/dt

Δ