IRFR/U4615PbF
10
Thermal Response ( Z thJC ) °C/W
1
D = 0.50
0.20
0.1
0.10
0.05
0.02
0.01
τ
J
R
1
R
1
τ
J
τ
1
τ
2
R
2
R
2
R
3
R
3
τ
3
R
4
R
4
τ
C
τ
τ
1
τ
2
τ
3
τ
4
τ
4
Ri (°C/W)
0.02324
0.26212
0.50102
0.25880
τi
(sec)
0.000008
0.000106
0.001115
0.005407
0.01
SINGLE PULSE
( THERMAL RESPONSE )
1E-005
0.0001
Ci=
τi/Ri
Ci i/Ri
Notes:
1. Duty Factor D = t1/t2
2. Peak Tj = P dm x Zthjc + Tc
0.001
0.01
0.1
0.001
1E-006
t1 , Rectangular Pulse Duration (sec)
Fig 13.
Maximum Effective Transient Thermal Impedance, Junction-to-Case
100
Duty Cycle = Single Pulse
Allowed avalanche Current vs avalanche
pulsewidth, tav, assuming
∆Tj
= 150°C and
Tstart =25°C (Single Pulse)
Avalanche Current (A)
10
0.01
0.05
0.10
1
Allowed avalanche Current vs avalanche
pulsewidth, tav, assuming
∆Τ
j = 25°C and
Tstart = 150°C.
0.1
1.0E-06
1.0E-05
1.0E-04
tav (sec)
1.0E-03
1.0E-02
1.0E-01
Fig 14.
Typical Avalanche Current vs.Pulsewidth
120
100
80
60
40
20
0
25
50
75
100
125
150
175
Starting T J , Junction Temperature (°C)
TOP
Single Pulse
BOTTOM 1.0% Duty Cycle
ID = 21A
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 16a, 16b.
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
Fig 15.
Maximum Avalanche Energy vs. Temperature
EAR , Avalanche Energy (mJ)
5 / 11
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