IRFB3256PBF Datasheet, PDF (5/9 Pages) International Rectifier – High Efficiency Synchronous Rectification in SMPS

1
0.1
0.01
D = 0.50
0.20
0.10
0.05
0.02
0.01
IRFB3256PbF
0.001
0.0001
1E-006
SINGLE PULSE
( THERMAL RESPONSE )
Notes:
1. Duty Factor D = t1/t2
2. Peak Tj = P dm x Zthjc + Tc
1E-005
0.0001
0.001
0.01
0.1
1
t1 , Rectangular Pulse Duration (sec)
Fig 13. Maximum Effective Transient Thermal Impedance, Junction-to-Case
1000
100
0.05
10
0.10
Duty Cycle = Single Pulse
0.01
Allowed avalanche Current vs avalanche
pulsewidth, tav, assuming ΔTj = 150°C and
Tstart =25°C (Single Pulse)
Allowed avalanche Current vs avalanche
pulsewidth, tav, assuming ΔΤ j = 25°C and
Tstart = 150°C.
1
1.0E-06
1.0E-05
1.0E-04
1.0E-03
1.0E-02
tav (sec)
Fig 14. Typical Avalanche Current vs.Pulsewidth
1.0E-01
400
TOP
Single Pulse
BOTTOM 1.0% Duty Cycle
ID = 75A
300
200
100
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. ΔT = 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)
0
25 50 75 100 125 150 175
Starting TJ , Junction Temperature (°C)
Fig 15. Maximum Avalanche Energy vs. Temperature
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
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