NOTE 3 — THERMAL CIRCUIT MODEL
(For heat conduction through the leads)
R
R
R
R
R
R
θS(K)
θ
S(A)
θ
L(A)
T
θ
J(A)
θ
J(K)
θ
L(K)
T
T
A(K)
A(A)
P
D
T
T
L(K)
T
T
L(A)
C(A)
J
C(K)
Use of the above model permits junction to lead thermal resistance
for any mounting configuration to be found. For a given total lead
length, lowest values occur when one side of the rectifier is brought
as close as possible to the heatsink. Terms in the model signify:
(Subscripts A and K refer to anode and cathode sides, respectively.)
Values for thermal resistance components are:
R
= 100°C/W/in typically and 120°C/W/in maximum
= 36°C/W typically and 46°C/W maximum.
θL
R
θJ
T
= Ambient Temperature
= Lead Temperature
T = Case Temperature
C
A
T
T = Junction Temperature
J
L
R
R
R
= Thermal Resistance, Heatsink to Ambient
= Thermal Resistance, Lead to Heatsink
= Thermal Resistance, Junction to Case
θS
θL
θJ
P
= Power Dissipation
D
125
115
1 Cycle
20
T
= 70°C
L
f = 60 Hz
10
105
95
7.0
T
= 100°C
C
5.0
85
3.0
2.0
Surge Applied at
Rated Load Conditions
25°C
75
1.0
2.0
3.0
5.0 7.0 10
20
30
40 70 100
NUMBER OF CYCLES
1.0
0.7
0.5
Figure 8. Maximum Non–Repetitive Surge Current
30
20
T
= 125°C
J
0.3
0.2
15
100°C
5.0
3.0
2.0
0.1
75°C
1.0
0.5
0.07
0.05
25°C
0.3
0.2
0.03
0.02
0.1
1N5817
1N5818
1N5819
0.05
0.03
0.1
0.2 0.3 0.4 0.5
0.6
0.7 0.8 0.9 1.0 1.1
0
4.0
8.0
12
16
20
24
28
32
36
40
v , INSTANTANEOUS FORWARD VOLTAGE (VOLTS)
F
V
, REVERSE VOLTAGE (VOLTS)
R
Figure 7. Typical Forward Voltage
Figure 9. Typical Reverse Current
4
Rectifier Device Data
MOTOROLA [ MOTOROLA ]
