BU323AP

3–4

Motorola Bipolar Power Transistor Device Data

Figure 9. Thermal Response

t, TIME (ms)

1

0.01

0.01

0.5

0.2

0.1

0.05

0.02

0.05

1

2

5

10

20

50

100

200

2000

500

R

θJC(t) = r(t) RθJC

R

θJC = °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

0.05

0.02

0.01

SINGLE PULSE

0.1

0.7

0.3

0.07

0.03

0.02

0.1

0.5

0.2

1000

50

5

Figure 10. Forward Bias Safe Operating Area

VCE, COLLECTOR–EMITTER VOLTAGE (VOLTS)

20

10

5

1

0.005

30

70

BONDING WIRE LIMIT

THERMAL LIMIT (SINGLE PULSE)

SECOND BREAKDOWN LIMIT

dc

100

µs

0.2

0.01

10

20

5.0 ms

1.0 ms

100

200 300

500

2

0.1

50

TC = 25°C

There are two limitations on the power handling ability of a

transistor average junction temperature and second break-

down. 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 dissipa-

tion than the curves indicate.

The data of Figure 10 is based on TC = 25_C, TJ(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 not der-

ate the same as thermal limitations. Allowable current at the

voltages shown on Figure 10 may be found at any case tem-

perature by using the appropriate curve on Figure 11.

TJ(pk) may be calculated from the data in Figure 11. At high

case temperatures, thermal limitations will reduce the power

that can be handled to values less than the limitations im-

posed by second breakdown.

100

0

Figure 11. Power Derating

TC, CASE TEMPERATURE (°C)

80

0

80

120

40

20

40

160

200

60

THERMAL

DERATING

SECOND BREAKDOWN

DERATING

Figure 12. Ignition Test Circuit

0 Vdc

t1

50 ms

≈ 1K

≈ 30

B

470

VCC = 16 Vdc

1N4001

BC337

47

VZ

C

E

TUT

2.2

0.22

µF

100

1N4001

<1

11 mH

INDUCTIVE LOAD

t1 to be selected such that IC reaches 10 Adc before switch–off.

NOTE: Figure 12 specifies energy handling capabilities in an automotive ignition circuit.

VZ = 350 V (BU323P)

at IZ = 20 mA