IRFB3507/IRFS3507/IRFSL3507
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Fig 13. Maximum Effective Transient Thermal Impedance, Junction-to-Case
Fig 14. Typical Avalanche Current vs.Pulsewidth
Fig 15. Maximum Avalanche Energy vs. Temperature
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
ZthJC(D, tav) = Transient thermal resistance, see Figures 13)
PD (ave) = 1/2 ( 1.3·BV·Iav) = DT/ ZthJC
Iav = 2DT/ [1.3·BV·Zth]
EAS (AR) = PD (ave)·tav
1E-006 1E-005 0.0001 0.001 0.01 0.1 1
t1 , R ectangular Pulse D ur ation ( sec)
0.0001
0.001
0.01
0.1
1
10
Thermal Response ( Z thJC )
0.20
0.10
D = 0.50
0.02
0.01
0.05
SINGLE PULSE
( THERMAL RESPONSE ) Notes:
1. Duty Factor D = t1/t2
2. Peak Tj = P dm x Zthj c + Tc
Ri (°C/W) τi (sec)
0.2963 0.000504
0.4738 0.013890
τJ
τJ
τ1
τ1τ2
τ2
R1
R1R2
R2
τ
Ci= τi/Ri
25 50 75 100 125 150 175
Starting TJ , Juncti on Temperature (°C)
0
50
100
150
200
250
300
EAR , Avalanche Energy (mJ)
TOP Sing le Pulse
BOTTOM 1% Duty Cycle
ID = 58A
1.0E-06 1.0E-05 1.0E-04 1.0E-03 1.0E-02 1.0E-01
tav (sec)
0.1
1
10
100
1000
Avalanche Current (A)
0.05
Dut y Cycle = Single Pulse
0.10
Allowed avalanche Current vs avalanche
pulsewidth, tav, assuming ∆Τ j = 25°C and
Tstart = 150°C .
0.01
Allowed avalanche Current vs avalanche
pulsewidth, tav, assuming ∆Tj = 150°C and
Tstart =25°C (Si ngle Pulse)
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