MR750 SERIES
IF(AV), AVERAGE FORWARD CURRENT (AMPS)
28
L = 1/8"
24
20
16
12
8.0
4.0
0
0
20
40
60
80
100
120
140
160
180
200
1/4"
3/8"
RESISTIVE INDUCTIVE
LOADS
BOTH LEADS TO HEAT
SINK WITH LENGTHS
AS SHOWN
5/8"
IF(AV), AVERAGE FORWARD CURRENT (AMPS)
7.0
6.0
5.0
4.0
3.0
2.0
1.0
0
0
20
40
R
qJA
= 40°C/W
SEE NOTE
6F (I
PK
/I
AVE
= 6.28)
60
80
100
120
140
160
180
200
R
qJA
= 25°C/W
SEE NOTE
RESISTIVE INDUCTIVE LOADS
CAPACITANCE LOADS − 1F & 3F
I
(pk)
= 5 I
avg
I
(pk)
= 10 I
avg
I
(pk)
= 20 I
avg
f = 60 Hz
T
L
, LEAD TEMPERATURE (°C)
T
A
, AMBIENT TEMPERATURE (°C)
Figure 5. Maximum Current Ratings
Figure 6. Maximum Current Ratings
NOTES
32
PF(AV), POWER DISSIPATION (WATTS)
28
24
20
16
12
8.0
4.0
0
0
4.0
8.0
12
16
20
24
28
32
RESISTIVE − INDUCTIVE LOADS
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
qS
= Thermal Resistance, Heat Sink to Ambient
R
qL
= Thermal Resistance, Lead to Heat Sink
R
qJ
= 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
qL
= 40°C/W/in. Typically and 44°C/W/in Maximum.
R
qJ
= 2°C/W typically and 4°C/W Maximum.
Since R
qJ
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
qJL
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
qJA
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.
CAPACITANCE LOADS
I
(pk)
= 5 I
avg
10 I
avg
20 I
avg
6F
1F & 3F
R
qS(A)
T
A(A)
T
L(A)
T
C(A)
T
J
THERMAL CIRCUIT MODEL
(For Heat Conduction Through The Leads)
R
qL(A)
R
qJ(A)
R
qJ(K)
P
F
T
C(K)
T
L(K)
R
qL(K)
R
qS(K)
T
A(K)
I
F(AV)
, AVERAGE FORWARD CURRENT (AMPS)
Figure 7. Power Dissipation
40
R
θ
JL , THERMAL RESISTANCE,
JUNCTION−TO−LEAD(
°
C/W)
35
30
25
20
15
10
5.0
0
0
1/8
1/4
3/8
1/2
5/8
3/4
7/8
1.0
L, LEAD LENGTH (INCHES)
BOTH LEADS TO HEAT
SINK, EQUAL LENGTH
SINGLE LEAD TO HEAT SINK,
INSIGNIFICANT HEAT FLOW
THROUGH OTHER LEAD
Figure 8. Steady State Thermal Resistance
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Board Ground Plane
Recommended mounting for half wave circuit
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