1N5820, 1N5821, 1N5822

www.onsemi.com

4

Figure 1. Maximum Reference Temperature

1N5820

Figure 2. Maximum Reference Temperature

1N5821

Figure 3. Maximum Reference Temperature

1N5822

Figure 4. Steady−State Thermal Resistance

15

2.0

VR, REVERSE VOLTAGE (VOLTS)

115

125

105

30

4.0

VR, REVERSE VOLTAGE (VOLTS)

125

115

105

95

85

75

L, LEAD LENGTH (INCHES)

1/8

0

25

20

15

10

5.0

0

2/8

40

95

85

75

5.0

3.0

4.0

7.0

10

20

5.0

7.0

10

15

20

3/8

4/8

5/8

6/8

7/8

1.0

40

35

30

BOTH LEADS TO HEATSINK,

EQUAL LENGTH

MAXIMUM

TYPICAL

RqJA (°C/W) = 70

50

40

28

20

15

10

8.0

15

VR, REVERSE VOLTAGE (VOLTS)

115

105

95

85

75

5.0

3.0

4.0

7.0

10

20

RqJA (°C/W) = 70

50

40

28

20

15

10

8.0

125

30

RqJA (°C/W) = 70

50

40

28

20

15

10

8.0

0.2

0.5

1.0

2.0

5.0

10

20

50

100

200

500

1.0 k

2.0 k

5.0 k

10 k

0.05

0.03

0.02

0.01

0.1

t, TIME (ms)

0.5

0.3

0.2

1.0

LEAD LENGTH = 1/4

″

Ppk

Ppk

tp

t1

TIME

DUTY CYCLE = tp/t1

PEAK POWER, Ppk, is peak of an

equivalent square power pulse.

DTJL = Ppk • RqJL [D + (1 - D) • r(t1 + tp) + r(tp) - r(t1)] where:

DTJL = the increase in junction temperature above the lead temperature.

r(t) = normalized value of transient thermal resistance at time, t, i.e.:

r(t1 + tp) = normalized value of transient thermal resistance at time

t1 + tp, etc.

Figure 5. Thermal Response

20 k

The temperature of the lead should be measured using a ther­

mocouple placed on the lead as close as possible to the tie point.

The thermal mass connected to the tie point is normally large

enough so that it will not significantly respond to heat surges

generated in the diode as a result of pulsed operation once

steady-state conditions are achieved. Using the measured val­

ue of TL, the junction temperature may be determined by:

TJ = TL + DTJL