AN2344

Datasheet avalanche ratings

17/27

By superimposition principle and the manipulation of Equation 11, the peak temperature

results from every single power pulse in Figure 11. may be expressed:

●

First pulse

Equation 13

●

Second pulse

Equation 14

●

Third pulse

Equation 15

Figure 12.

Thermal response comparison

Using ST’s MDMesh STP11NM60FP as an actual example, Figure 13. shows the switching

waveforms of the device as it is applied as a main switch in an AC adapter. They are also

waveforms detailing the avalanche phenomenon.

Table 2.

Rectangular approximation of special power curves

Curve

P(t)

see Appendix A on page 24

Energy

t

P’

Ramp

Triangular

Figure 21.

Parabolic

2

T

JC max1

()

P

Zth

t

D1

+

()

–

() 0.7 P

1

•

Zth

()

•

+

=

∆

*

*

T

JC max1

()

P

Zth

t

2

+

()

–

() 0.89 P

2

•

Zth

()

•

+

=

∆

* +

0.7

P

1

•

Zth

t

D1

t

2

+

–

() Zth

t

2

+

()

–

[]

•

+

T

JCmax1

P

Zth

t

2

t

D3

t

3

++

+

()

–

() 0.7 P

3

•

Zth

()

•

+

=

∆

*

* +

0.7

P

1

•

Zth

t

D1

t

2

t

3

t

D3

++

+

–

() Zth

t

2

t

3

t

D3

++

+

()

–

[]

•

+

*

*

+

0.89

P

2

•

Zth

t

3

t

D3

++

() Zth

t

D3

+

()

–

•

*

*

*

+