IRFS7434-7PPbF
1
0.1
D = 0.50
0.20
0.10
0.05
0.02
0.01
0.01
SINGLE PULSE
( THERMAL RESPONSE )
0.001
Notes:
1. Duty Factor D = t1/t2
2. Peak Tj = P dm x Zthjc + Tc
0.0001
1E-006
1E-005
0.0001
0.001
0.01
0.1
t
, Rectangular Pulse Duration (sec)
1
Fig 14. Maximum Effective Transient Thermal Impedance, Junction-to-Case
1000
100
10
Duty Cycle = Single Pulse
Allowed avalanche Current vs avalanche
pulsewidth, tav, assuming Tj = 125°C and
Tstart =25°C (Single Pulse)
0.01
0.05
0.10
Allowed avalanche Current vs avalanche
pulsewidth, tav, assuming j = 25°C and
Tstart = 125°C.
1
1.0E-06
1.0E-05
1.0E-04
1.0E-03
1.0E-02
1.0E-01
tav (sec)
Fig 15. Typical Avalanche Current vs. Pulse width
400
350
300
250
200
150
100
50
Notes on Repetitive Avalanche Curves , Figures 14, 15:
(For further info, see AN-1005 at www.irf.com)
1.Avalanche failures assumption:
TOP
Single Pulse
BOTTOM 1.0% Duty Cycle
I
= 100A
D
Purely a thermal phenomenon and failure occurs at a
temperature far in excess of Tjmax. This is validated for every
part type.
2. Safe operation in Avalanche is allowed as long asTjmax is not
exceeded.
3. Equation below based on circuit and waveforms shown in Figures
23a, 23b.
4. PD (ave) = Average power dissipation per single avalanche pulse.
5. BV = Rated breakdown voltage (1.3 factor accounts for voltage
increase during avalanche).
6. Iav = Allowable avalanche current.
7. T = Allowable rise in junction temperature, not to exceed Tjmax
(assumed as 25°C in Figure 14, 15).
tav = Average time in avalanche.
0
D = Duty cycle in avalanche = tav ·f
ZthJC(D, tav) = Transient thermal resistance, see Figures 13)
25
50
75
100
125
150
Starting T , Junction Temperature (°C)
J
PD (ave) = 1/2 ( 1.3·BV·Iav) = T/ ZthJC
I
av = 2T/ [1.3·BV·Zth]
EAS (AR) = PD (ave)· av
t
Fig 16. Maximum Avalanche Energy vs. Temperature
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November 19, 2014
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