Tch ( ) = Ta + Pa •
r
ch-c (Tn + T + t
1
+ t
2
+ t
3
)
+ (P
1
– Pa) •
r
ch-c (T + t
1
+ t
2
+ t
3
)
– (P
1
– P
2
) •
r
ch-c (T + t
2
+ t
3
)
+ (P
3
– P
2
) •
r
ch-c (T + t
3
)
– P
3
•
r
ch-c (T) + P
4
•
r
ch-c (t
4
+ t
5
+ t
6
)
– (P
4
– P
5
) •
r
ch-c (t
5
+ t
6
)
......................................
3
+ (P
6
– P
5
) •
r
ch-c (t
6
)
: Ambient temperature
*
Ta
r
ch-c ( t): Transient thermal resistance at pulse width t
Tch (
1
)
= Ta + Pa •
r
ch-c (Tn + T' + t
1
+ t
2
+ t
3
)
+ (P
1
– Pa) •
r
ch-c (T' + t
1
+ t
2
+ t
3
)
– (P
1
– P
2
) •
r
ch-c (T '+ t
2
+ t
3
)
+ (P
3
– P
2
) •
r
ch-c (T' + t
3
)
– P
3
•
r
ch-c (T') + P
4
•
r
ch-c (t
4
+ t
5
+ t
6
)
– (P
4
– P
5
) •
r
ch-c (t
5
+ t
6
)
+ (P
6
– P
5
) •
r
ch-c (t
6
) ......................................
4
Then calculate the channel temperature Tch (
diately before avalanche.
1
)
imme-
This Tch (
1
) value becomes Tch (start). If the avalanche
energy (E
AS
= P
6
• t
6
) is within the value derated from the
guaranteed E
AS
value at the temperature, there is no
problem as far as the avalanche energy is concerned.
Fig. C
Transient
Stationary
Fig. D
P
3
P
1
P
4
P
2
P
5
P
6
V
DS
I
D
Pa
0
T(n)
T(n)
t
1
t
2
t
3
t
4
T
T'
t
5
t
6
0
1
Avalanche in this section
Avalanche energy capability measuring method
Fig. 1
L
I
L
V
DS
V
GS
0V
R
G
V
DD
I
L
V
DS
E
AS
=
V
(BR) DSS
1
• L • I
Lp2
•
2
V
(BR) DSS
– V
DD
I
Lp
V
(BR) DSS
V
DD
(a) Measuring circuit
(b)
Output waveform
Switching time measuring method
Fig. 2
Nch
(a) Measuring circuit
R
L
I
D
V
DS
V
GS
R
G
0V
V
DD
(b) Input-output waveform
90%
V
GS
10%
90%
V
DS
10%
P.W. = 10µs
Duty cycle 1%
t
d(on)
t
r
t
on
t
d(off)
t
f
t
off
Fig. 3
Pch
R
L
I
D
V
DS
0V
R
G
V
GS
P.W. = 10µs
Duty cycle < 1%
V
DD
10%
V
GS
90%
10%
V
DS
90%
t
d(on)
t
r
t
on
t
d(off)
t
f
t
off
5
SANKEN [ SANKEN ELECTRIC ]
