IRFB7437PbF
1
D = 0.50
Thermal Response ( Z thJC )
0.1
0.20
0.10
0.05
0.02
0.01
0.01
0.001
SINGLE PULSE
( THERMAL RESPONSE )
Notes:
1. Duty Factor D = t1/t2
2. Peak Tj = P dm x Zthjc + Tc
0.0001
0.001
0.01
0.1
0.0001
1E-006
1E-005
t1 , Rectangular Pulse Duration (sec)
Fig 14.
Maximum Effective Transient Thermal Impedance, Junction-to-Case
1000
Avalanche Current (A)
100
Allowed avalanche Current vs avalanche
pulsewidth, tav, assuming
Tj
= 150°C and
Tstart =25°C (Single Pulse)
10
Allowed avalanche Current vs avalanche
pulsewidth, tav, assuming
j = 25°C and
Tstart = 150°C. (Single Pulse)
1
1.0E-06
1.0E-05
1.0E-04
tav (sec)
1.0E-03
1.0E-02
1.0E-01
Fig 15.
Typical Avalanche Current vs.Pulsewidth
350
300
EAR , Avalanche Energy (mJ)
TOP
Single Pulse
BOTTOM 1% Duty Cycle
ID = 100A
250
200
150
100
50
0
25
50
75
100
125
150
175
Notes on Repetitive Avalanche Curves , Figures 14, 15:
(For further info, see AN-1005 at www.irf.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 asT
jmax
is not exceeded.
3. Equation below based on circuit and waveforms shown in Figures 22a, 22b.
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 T
jmax
(assumed as
25°C in Figure 14, 15).
t
av =
Average time in avalanche.
D = Duty cycle in avalanche = t
av
·f
Z
thJC
(D, t
av
) = Transient thermal resistance, see Figures 13)
P
D (ave)
= 1/2 ( 1.3·BV·I
av
) =
DT/
Z
thJC
I
av
= 2DT/ [1.3·BV·Z
th
]
E
AS (AR)
= P
D (ave)
·t
av
Starting TJ , Junction Temperature (°C)
Fig 16.
Maximum Avalanche Energy vs. Temperature
6
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