IRF/B/S/SL4310
1
0.1
D = 0.50
0.20
0.10
0.05
R1
R2
R1
R2
Ri (°C/W) τi (sec)
0.1962 0.00117
τ
0.01
J τJ
τ
0.02
0.01
τ
Cτ
1 τ1
Ci= τi/Ri
τ
2τ2
0.2542 0.016569
0.001
Notes:
1. Duty Factor D = t1/t2
2. Peak Tj = P dm x Zthjc + Tc
SINGLE PULSE
( THERMAL RESPONSE )
0.0001
1E-006
1E-005
0.0001
0.001
0.01
0.1
t
, Rectangular Pulse Duration (sec)
1
Fig 13. Maximum Effective Transient Thermal Impedance, Junction-to-Case
100
10
1
Allowed avalanche Current vs avalanche
pulsewidth, tav, assuming ∆Tj = 150°C
and Tstart =25°C (Single Pulse)
Duty Cycle = Single Pulse
0.01
0.05
0.10
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
800
600
400
200
0
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 Tjmax. This is validated for every part type.
2. Safe operation in Avalanche is allowed as long as neither Tjmax nor
Iav (max) is exceeded.
3. Equation below based on circuit and waveforms shown in Figures 16a, 16b.
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.
D = Duty cycle in avalanche = tav ·f
TOP
BOTTOM 1% Duty Cycle
= 75A
Single Pulse
I
D
ZthJC(D, tav) = Transient thermal resistance, see Figures 13)
25
50
75
100
125
150
175
PD (ave) = 1/2 ( 1.3·BV·Iav) = DT/ ZthJC
Starting T , Junction Temperature (°C)
J
Iav = 2DT/ [1.3·BV·Zth]
EAS (AR) = PD (ave)·tav
Fig 15. Maximum Avalanche Energy vs. Temperature
5 / 11
www.freescale.net.cn
FREESCALE [ Freescale ]
