6
Motorola TMOS Power MOSFET Transistor Device Data
I
t, TIME
Figure 11. Reverse Recovery Time (trr)
Standard Cell Density
trr
High Cell Density
trr
tb
ta
SAFE OPERATING AREA
The Forward Biased Safe Operating Area curves define
the maximum simultaneous drain–to–source voltage and
drain current that a transistor can handle safely when it is for-
ward biased. Curves are based upon maximum peak junc-
tion temperature and a case temperature (TC) of 25
°
C. Peak
repetitive pulsed power limits are determined by using the
thermal response data in conjunction with the procedures
discussed in AN569, “Transient Thermal Resistance–General
Data and Its Use.”
Switching between the off–state and the on–state may tra-
verse any load line provided neither rated peak current (IDM)
nor rated voltage (VDSS) is exceeded and the transition time
(tr,tf) do not exceed 10
μ
s. In addition the total power aver-
aged over a complete switching cycle must not exceed
(TJ(MAX) – TC)/(R
θ
JC).
A Power MOSFET designated E–FET can be safely used
in switching circuits with unclamped inductive loads. For reli-
able operation, the stored energy from circuit inductance dis-
sipated in the transistor while in avalanche must be less than
the rated limit and adjusted for operating conditions differing
from those specified. Although industry practice is to rate in
terms of energy, avalanche energy capability is not a con-
stant. The energy rating decreases non–linearly with an in-
crease of peak current in avalanche and peak junction
temperature.
Although many E–FETs can withstand the stress of drain–
to–source avalanche at currents up to rated pulsed current
(IDM), the energy rating is specified at rated continuous cur-
rent (ID), in accordance with industry custom. The energy rat-
ing must be derated for temperature as shown in the
accompanying graph (Figure 12). Maximum energy at cur-
rents below rated continuous ID can safely be assumed to
equal the values indicated.
TJ, STARTING JUNCTION TEMPERATURE (
°
C)
EA
Figure 12. Maximum Rated Forward Biased
Safe Operating Area
0.1
1.0
100
VDS, DRAIN–TO–SOURCE VOLTAGE (VOLTS)
Figure 13. Maximum Avalanche Energy versus
Starting Junction Temperature
0.1
10
A
I
RDS(on) LIMIT
THERMAL LIMIT
PACKAGE LIMIT
0
25
50
75
100
125
80
40
ID = 75 A
1000
1.0
10
150
VGS = 10 V
SINGLE PULSE
TC = 25
°
C
240
120
280
dc
160
100
10 ms
1.0 ms
200