MJE16106
7
Motorola Bipolar Power Transistor Device Data
t, TIME (ms)
1
0.01
0.01
0.7
0.2
0.1
0.05
0.02
r(t), TRANSIENT THERMAL RESISTANCE
0.05 1 2 5 10 20 50 100 200 500
Z
θ
JC(t)
= r(t) R
θ
JC
R
θ
JC
= 1.0 OR 1.25
°
C/W MAX
D CURVES APPLY FOR POWER
PULSE TRAIN SHOWN
READ TIME AT t
1
T
J(pk)
– TC = P
(pk)
Z
θ
JC
P
(pk)
t
1
t
2
DUTY CYCLE, D = t1/t
2
D = 0.5
0.2
0.05
SINGLE PULSE
0.1
0.1 0.50.2
(NORMALIZED)
1.0 k
0.5
0.3
0.07
0.03
0.02
Figure 17. Power Derating
TC, CASE TEMPERATURE (°C)
Figure 18. Typical Thermal Response [Z
θJC
(t)]
100
0
0
120
POWER DERATING FACTOR (%)
40 200
80
80
40
20
THERMAL
DERATING
60
160
SECOND BREAKDOWN
DERATING
0.02
0.01
SAFE OPERATING AREA INFORMATION
FORWARD BIAS
There are two limitations on the power handling ability of a
transistor: average junction temperature and second breakdown. Safe operating area curves indicate IC – VCE limits of
the transistor that must be observed for reliable operation;
i.e., the transistor must not be subjected to greater dissipation than the curves indicate.
The data in Figure 14 is based on TC = 25_C; T
J(pk)
is
variable depending on power level. Second breakdown pulse
limits are valid for duty cycles to 10% but must be derated
when TC ≥ 25_C. Second breakdown limitations do n ot
derate the same as thermal limitations. Allowable current at
the voltages shown on Figure 14 may be found at any case
temperature by using the appropriate curve on Figure 17.
T
J(pk)
may be calculated from the data in Figure 18. At high
case temperatures, thermal limitations will reduce the power
that can be handled to values less than the limitations imposed by second breakdown.
REVERSE BIAS
For inductive loads, high voltage and high current must be
sustained simultaneously during turn–off, in most cases, with
the base–to–emitter junction reverse biased. Under these
conditions the collector voltage must be held to a safe level
at or below a specific value of collector current. This can be
accomplished by several means such as active clamping,
RC snubbing, load line shaping, etc. The safe level for these
devices is specified as Reverse Biased Safe Operating Area
and represents the voltage–current condition allowable during reverse biased turn–off. This rating is verified under
clamped conditions so that the device is never subjected to
an avalanche mode. Figure 15 gives the RBSOA characteristics.
SWITCHMODE III DESIGN CONSIDERATIONS
FBSOA
Allowable dc power dissipation in bipolar power transistors
decreases dramatically with increasing collector–emitter
voltage. A transistor which safely dissipates 100 watts at
10 volts will typically dissipate less than 10 watts at its rated
V
(BR)CEO(sus)
. From a power handling point of view, current
and voltage are not interchangeable (see Application Note
AN875).