AUIRF7484Q
8 2015-11-16
Fig 19. Typical Avalanche Current vs. Pulse width
Notes on Repetitive Avalanche Curves , Figures 19, 20:
(For further info, see AN-1005 at www.infineon.com)
1. Avalanche failures assumption:
Purely a thermal phenomenon and failure occurs at a temperature far in
excess of T
jmax. This is validated for every part type.
2. Safe operation in Avalanche is allowed as long as T
jmax is not exceeded.
3. Equation below based on circuit and waveforms shown in Figures 16b, 16c.
4. P
D (ave) = Average power dissipation per single avalanche pulse.
5. BV = Rated breakdown voltage (1.3 factor accounts for voltage increase
during avalanche).
6. I
av = Allowable avalanche current.
7. T
= Allowable rise in junction temperature, not to exceed Tjmax (assumed as
25°C in Figure 11, 16).
t
av = Average time in avalanche.
D = Duty cycle in avalanche = t
av ·f
Z
thJC(D, tav) = Transient thermal resistance, see Figures 11)
P
D (ave)
= 1/2 ( 1.3·BV·I
av
) = T/ Z
thJC
I
av
= 2T/ [1.3·BV·Z
th
]
E
AS (AR)
= P
D (ave)
·t
av
Fig 20. Maximum Avalanche Energy
vs. Temperature
1.0E-06 1.0E-05 1.0E-04 1.0E-03 1.0E-02 1.0E-01 1.0E+00 1.0E+01 1.0E+02 1.0E+03
tav (sec)
0.01
0.1
1
10
100
A
v
a
l
a
n
c
h
e
C
u
r
r
e
n
t
(
A
)
0.05
Duty Cycle = Single Pulse
0.10
Allowed avalanche Current vs
avalanche pulsewidth, tav
assuming
Tj = 25°C due to
avalanche losses
0.01
25 50 75 100 125 150
Starting T
J
, Junction Temperature (°C)
0
25
50
75
100
125
150
175
200
225
250
E
A
R
,
A
v
a
l
a
n
c
h
e
E
n
e
r
g
y
(
m
J
)
TOP Single Pulse
BOTTOM 10% Duty Cycle
I
D
= 14A
