IRF2805LPBF datasheet(7/11 Pages) IRF

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IRF2805S/LPbF

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Fig 15. Typical Avalanche Current Vs.Pulsewidth

Fig 16. Maximum Avalanche Energy

Vs. Temperature

Notes on Repetitive Avalanche Curves , Figures 15, 16:

(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 12a, 12b.

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 15, 16).

tav = Average time in avalanche.

D = Duty cycle in avalanche = tav ·f

ZthJC(D, tav) = Transient thermal resistance, see figure 11)

PD (ave) = 1/2 ( 1.3·BV·Iav) = DT/ ZthJC

Iav = 2

DT/ [1.3·BV·Zth]

EAS (AR) = PD (ave)·tav

100

125

150

175

Starting TJ , Junction Temperature (°C)

100

200

300

400

TOP

Single Pulse

BOTTOM 10% Duty Cycle

ID = 104A

1.0E-07

1.0E-06

1.0E-05

1.0E-04

1.0E-03

1.0E-02

1.0E-01

tav (sec)

0.1

100

1000

10000

0.05

Duty Cycle = Single Pulse

0.10

Allowed avalanche Current vs

avalanche

pulsewidth,

tav

assuming ∆ Tj = 25°C due to

avalanche losses. Note: In no

case should Tj be allowed to

exceed Tjmax

0.01

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