MR750 SERIES
http://onsemi.com
4
Figure 5. Maximum Current Ratings
T
L
, LEAD TEMPERATURE (°C)
0
8.0
I
F(AV)
0
12
20
28
40 80 120 160 200
Figure 6. Maximum Current Ratings
0 8.0
4.0
0
16 24 32
I
F(AV)
, AVERAGE FORWARD CURRENT (AMPS)
P
F(AV)
Figure 7. Power Dissipation
, POWER DISSIPATION (WATTS)
5/8"
, AVERAGE FORWARD CURRENT (AMPS)
CAPACITANCE LOADS
8.0
12
16
RESISTIVE INDUCTIVE
LOADS
T
A
, AMBIENT TEMPERATURE (°C)
0
1.0
I
F(AV)
0
2.0
3.0
4.0
40 80 120 160 200
Figure 8. Steady State Thermal Resistance
f = 60 Hz
, AVERAGE FORWARD CURRENT (AMPS)
RESISTIVE INDUCTIVE LOADS
CAPACITANCE LOADS − 1 & 3
20
6
1 & 3
20 I
avg
T
A(A)
T
A(K)
T
L(A)
T
C(A)
T
J
T
C(K)
T
L(K)
P
F
R
S(A)
R
L(A)
R
J(A)
R
J(K)
R
L(K)
R
S(K)
Use of the above model permits junction to lead thermal resistance for
any mounting configuration to be found. Lowest values occur when one
side of the rectifier is brought as close as possible to the heat sink as
shown below. Terms in the model signify:
T
A
= Ambient Temperature T
C
= Case Temperature
T
L
= Lead Temperature T
J
= Junction Temperature
R
S
= Thermal Resistance, Heat Sink to Ambient
R
L
= Thermal Resistance, Lead to Heat Sink
R
J
= Thermal Resistance, Junction to Case
P
F
= Power Dissipation
(Subscripts A and K refer to anode and cathode sides, respectively.)
Values for thermal resistance components are:
R
L
= 40°C/W/in. Typically and 44°C/W/in Maximum.
R
J
= 2°C/W typically and 4°C/W Maximum.
Since R
J
is so low, measurements of the case temperature, T
C
, will be
approximately equal to junction temperature in practical lead mounted
applications. When used as a 60 Hz rectifierm the slow thermal response
holds T
J(PK)
close to T
J(AVG)
. Therefore maximum lead temperature may
be found from: T
L
= 175°−R
JL
P
F
. P
F
may be found from Figure 7.
The recommended method of mounting to a P.C. board is shown on the
sketch, where R
JA
is approximately 25°C/W for a 1−1/2" x 1−1/2" copper
surface area. Values of 40°C/W are typical for mounting to terminal strips
or P.C. boards where available surface area is small.
Board Ground Plane
Recommended mounting for half wave circuit
24
28
32
0 1/4
5.0
0
1/2 3/4 1.0
L, LEAD LENGTH (INCHES)
R
JL
, THERMAL RESISTANCE,
SINGLE LEAD TO HEAT SINK,
INSIGNIFICANT HEAT FLOW
THROUGH OTHER LEAD
10
15
20
25
30
35
40
24
16
4.0
20 60 100 140 180
4.0 12 20 28
1/8 3/8 5/8 7/8
θ
JUNCTION−TO−LEAD( C/W)
°
BOTH LEADS TO HEAT
SINK WITH LENGTHS
AS SHOWN
3/8"
1/4"
L = 1/8"
20 60 100 140 180
5.0
6.0
7.0
I
(pk)
= 5 I
avg
I
(pk)
= 10 I
avg
I
(pk)
= 20 I
avg
10 I
avg
I
(pk)
= 5 I
avg
RESISTIVE − INDUCTIVE LOADS
BOTH LEADS TO HEAT
SINK, EQUAL LENGTH
6 (I
PK
/I
AVE
= 6.28)
SEE NOTE
R
JA
= 40°C/W
SEE NOTE
R
JA
= 25°C/W
NOTES
THERMAL CIRCUIT MODEL
(For Heat Conduction Through The Leads)
