125

115

105

95

85

75

20

15

10

7.0

5.0

4.0

3.0

2.0

°

VR, DC REVERSE VOLTAGE (VOLTS)

Figure 1. Maximum Reference Temperature

1N5817

40

30

23

60

80

R

θJA (°C/W) = 110

125

115

105

95

85

75

20

15

10

7.0

5.0

30

4.0

3.0

40

30

23

R

θJA (°C/W) = 110

80

60

Figure 2. Maximum Reference Temperature

1N5818

125

115

105

95

85

75

20

15

10

7.0

5.0

30

4.0

40

R

θJA (°C/W) = 110

60

80

Figure 3. Maximum Reference Temperature

1N5819

Circuit

Load

Half Wave

Resistive

Capacitive*

Full Wave, Bridge

Resistive

Capacitive

Full Wave, Center Tapped* †

Resistive

Capacitive

Sine Wave

Square Wave

0.5

0.75

1.3

1.5

0.5

0.75

0.65

0.75

1.0

1.5

1.3

1.5

40

30

23

°

VR, DC REVERSE VOLTAGE (VOLTS)

VR, DC REVERSE VOLTAGE (VOLTS)

*Note that VR(PK) ≈ 2.0 Vin(PK).

Table 1. Values for Factor F

°

1N5817 1N5818 1N5819

2

Rectifier Device Data

NOTE 1 — 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) =

where TA(max) =

TJ(max) =

PF(AV) =

PR(AV) =

R

θJA =

TJ(max) – R

θJAPF(AV) – RθJAPR(AV)

Maximum allowable ambient temperature

Maximum allowable junction temperature

(1)

Average forward power dissipation

(125

°C or the temperature at which thermal

runaway occurs, whichever is lowest)

Average reverse power dissipation

Junction–to–ambient thermal resistance

Figures 1, 2, and 3 permit easier use of equation (1) by taking re-

verse power dissipation and thermal runaway into consideration. The

figures solve for a reference temperature as determined by equation

(2).

TR = TJ(max) – R

θJAPR(AV)

(2)

Substituting equation (2) into equation (1) yields:

TA(max) = TR – R

θJAPF(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 condi-

tion 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 com-

mon rectifier circuits, Table 1 indicates suggested factors for an equiv-

alent dc voltage to use for conservative design, that is:

(4)

VR(equiv) = Vin(PK) x F

The factor F is derived by considering the properties of the various rec-

tifier circuits and the reverse characteristics of Schottky diodes.

EXAMPLE: Find TA(max)for1N5818operatedina12–voltdcsupply

using a bridge circuit with capacitive filter such that IDC=0.4A(IF(AV)=

0.5 A), I(FM)/I(AV) = 10, Input Voltage = 10 V(rms), R

θJA = 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

θJA = 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).

**Values given are for the 1N5818. Power is slightly lower for the

1N5817 because of its lower forward voltage, and higher for the

1N5819.