IRFS7440PbF datasheet(6/11 Pages) IRF

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IRFS/SL7440PbF

www.irf.com

October 10, 2012

Fig 14. Maximum Effective Transient Thermal Impedance, Junction-to-Case

Fig 15. Typical Avalanche Current vs.Pulsewidth

Fig 16. 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 asTjmax is not 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.

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

t1 , Rectangular Pulse Duration (sec)

0.001

0.01

0.1

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 Zthjc + Tc

100

125

150

175

Starting TJ , Junction Temperature (°C)

100

150

200

250

TOP

Single Pulse

BOTTOM 1.0% Duty Cycle

ID = 100A

1.0E-06

1.0E-05

1.0E-04

1.0E-03

1.0E-02

1.0E-01

tav (sec)

100

1000

Allowed avalanche Current vs avalanche

pulsewidth, tav, assuming

 j = 25°C and

Tstart = 150°C.

Allowed avalanche Current vs avalanche

pulsewidth, tav, assuming

Tj = 150°C and

Tstart =25°C (Single Pulse)

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