BUX48 BUX48A

3–407

Motorola Bipolar Power Transistor Device Data

t, TIME (ms)

1

0.01

0.02

0.5

0.2

0.1

0.05

0.02

0.05

1

2

5

10

20

50

100

200

500

R

θJC(t) = r(t) RθJC

θJC = 1°C/W MAX

D CURVES APPLY FOR POWER

PULSE TRAIN SHOWN

READ TIME AT t1

TJ(pk) – TC = P(pk) R

θJC(t)

P(pk)

t1

t2

DUTY CYCLE, D = t1/t2

D = 0.5

0.2

0.01

SINGLE PULSE

0.1

0.1

0.5

0.2

1000

2000

Figure 15. Thermal Response

SINGLE

PULSE

0.05

0.02

OVERLOAD CHARACTERISTICS

0

Figure 16. Rated Overload Safe Operating Area

(OLSOA)

VCE, COLLECTOR–EMITTER VOLTAGE (VOLTS)

300

100

40

60

500

100

400

TC = 25°C

450

200

20

tp = 10 µs

BUX48

BUX48A

80

OLSOA

OLSOA applies when maximum collector current is limited

and known. A good example is a circuit where an inductor is

inserted between the transistor and the bus, which limits the

rate of rise of collector current to a known value. If the tran-

sistor is then turned off within a specified amount of time, the

magnitude of collector current is also known.

Maximum allowable collector–emitter voltage versus col-

lector current is plotted for several pulse widths. (Pulse width

is defined as the time lag between the fault condition and the

removal of base drive.) Storage time of the transistor has

been factored into the curve. Therefore, with bus voltage and

maximum collector current known, Figure 16 defines the

maximum time which can be allowed for fault detection and

shutdown of base drive.

OLSOA is measured in a common–base circuit (Figure 18)

which allows precise definition of collector–emitter voltage

and collector current. This is the same circuit that is used to

measure forward–bias safe operating area.

0

Figure 17. IC = f(dV/dt)

dV/dt (KV/

µs)

2

4

4

2

5

6

8

10

3

1

500

µF

500 V

VEE

VCC

Figure 18. Overload SOA Test Circuit

Notes:

• VCE = VCC + VBE

• Adjust pulsed current source

for desired IC, tp

RBE = 100 Ω

RBE = 10 Ω

RBE = 2.2 Ω

RBE = 0