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1N5817RLG View Datasheet(PDF) - ON Semiconductor

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1N5817RLG Datasheet PDF : 7 Pages
1 2 3 4 5 6 7
1N5817, 1N5818, 1N5819
NOTE 3. — DETERMINING MAXIMUM RATINGS
Reverse power dissipation and the possibility of thermal
runaway must be considered when operating this rectifier at
reverse voltages above 0.1 VRWM. Proper derating may be
accomplished by use of equation (1).
TA(max) = TJ(max) − RqJAPF(AV) − RqJAPR(AV)
(1)
where TA(max) = Maximum allowable ambient temperature
TJ(max) = Maximum allowable junction temperature
(125°C or the temperature at which thermal
runaway occurs, whichever is lowest)
PF(AV) = Average forward power dissipation
PR(AV) = Average reverse power dissipation
RqJA = Junction−to−ambient thermal resistance
Figures 1, 2, and 3 permit easier use of equation (1) by
taking reverse power dissipation and thermal runaway into
consideration. The figures solve for a reference temperature
as determined by equation (2).
TR = TJ(max) − RqJAPR(AV)
(2)
Substituting equation (2) into equation (1) yields:
TA(max) = TR − RqJAPF(AV)
(3)
Inspection of equations (2) and (3) reveals that TR is the
ambient temperature at which thermal runaway occurs or
where TJ = 125°C, when forward power is zero. The
transition from one boundary condition to the other is
evident on the curves of Figures 1, 2, and 3 as a difference
in the rate of change of the slope in the vicinity of 115°C. The
data of Figures 1, 2, and 3 is based upon dc conditions. For
use in common rectifier circuits, Table 1 indicates suggested
factors for an equivalent dc voltage to use for conservative
design, that is:
VR(equiv) = Vin(PK) x F
(4)
The factor F is derived by considering the properties of the
various rectifier circuits and the reverse characteristics of
Schottky diodes.
EXAMPLE: Find TA(max) for 1N5818 operated in a
12−volt dc supply using a bridge circuit with capacitive filter
such that IDC = 0.4 A (IF(AV) = 0.5 A), I(FM)/I(AV) = 10, Input
Voltage = 10 V(rms), RqJA = 80°C/W.
Step 1. Find VR(equiv). Read F = 0.65 from Table 1,
Step 1. Find VR(equiv) = (1.41)(10)(0.65) = 9.2 V.
Step 2. Find TR from Figure 2. Read TR = 109°C
Step 1. Find @ VR = 9.2 V and RqJA = 80°C/W.
Step 3. Find PF(AV) from Figure 4. **Read PF(AV) = 0.5 W
@
I(FM)
I(AV)
= 10 and IF(AV) = 0.5 A.
Step 4. Find TA(max) from equation (3).
Step 4. Find TA(max) = 109 − (80) (0.5) = 69°C.
**Values given are for the 1N5818. Power is slightly lower for the
1N5817 because of its lower forward voltage, and higher for the
1N5819.
125
° 115
105
95
85
40 30 23
RqJA (°C/W) = 110
80
60
75
2.0
3.0 4.0 5.0
7.0
10
15 20
VR, DC REVERSE VOLTAGE (VOLTS)
Figure 1. Maximum Reference Temperature
1N5817
125
° 115
40 30 23
105
RqJA (°C/W) = 110
95
80 60
85
75
3.0 4.0 5.0
7.0
10
15
20
30
VR, DC REVERSE VOLTAGE (VOLTS)
Figure 2. Maximum Reference Temperature
1N5818
125
40
30
° 115
23
105 RqJA (°C/W) = 110
80
95
60
85
754.0 5.0
7.0
10
15
20
30 40
VR, DC REVERSE VOLTAGE (VOLTS)
Figure 3. Maximum Reference Temperature
1N5819
Table 1. Values for Factor F
Circuit
Half Wave
Full Wave, Bridge
Load
Resistive
Capacitive*
Resistive
Capacitive
Sine Wave
0.5
Square Wave
0.75
**Note that VR(PK) 2.0 Vin(PK).
1.3
0.5
0.65
1.5
0.75
0.75
†Use line to center tap voltage for Vin.
Full Wave, Center Tapped* †
Resistive
Capacitive
1.0
1.3
1.5
1.5
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