1
IRF/B/S/SL4310
D = 0.50
0.20
0.10
0.05
τ
J
R
1
R
1
τ
J
τ
1
τ
2
R
2
R
2
τ
C
τ
1
τ
2
τ
Thermal Response ( ZthJC )
0.1
0.01
0.02
0.01
Ri (°C/W)
τi
(sec)
0.1962 0.00117
0.2542
0.016569
0.001
Ci=
τi/Ri
Ci= i/Ri
SINGLE PULSE
( THERMAL RESPONSE )
0.0001
1E-006
1E-005
0.0001
0.001
Notes:
1. Duty Factor D = t1/t2
2. Peak Tj = P dm x Zthjc + Tc
0.01
0.1
t1 , Rectangular Pulse Duration (sec)
Fig 13.
Maximum Effective Transient Thermal Impedance, Junction-to-Case
100
Duty Cycle = Single Pulse
Avalanche Current (A)
0.01
0.05
0.10
Allowed avalanche Current vs avalanche
pulsewidth, tav, assuming
∆
Tj = 150°C
and Tstart =25°C (Single Pulse)
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
1.0E-03
1.0E-02
1.0E-01
tav (sec)
Fig 14.
Typical Avalanche Current vs.Pulsewidth
1000
EAR , Avalanche Energy (mJ)
800
TOP
Single Pulse
BOTTOM 1% Duty Cycle
ID = 75A
600
400
200
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 as neither T
jmax
nor
Iav (max) is 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
Starting TJ , Junction Temperature (°C)
Fig 15.
Maximum Avalanche Energy vs. Temperature
5 / 11
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