RDF50 Series

www.xppower.com

4

DC-DC Converter

Application Notes

Trim Up

%

5 V

12 V

24 V

48 V

Rtrim_up (k

Ω)

1

50.45

154.1

164.0

147.3

2

24.34

74.95

78.64

71.29

3

15.63

48.56

50.18

45.93

4

11.28

35.37

35.94

33.24

5

8.67

27.45

27.40

25.63

6

6.93

22.17

21.71

20.56

7

5.69

18.41

17.64

16.94

8

4.75

15.58

14.59

14.22

9

4.03

13.38

12.22

12.10

10

3.45

11.62

10.32

10.41

Trim Up

%

5 V

12 V

24 V

48 V

Rtrim_down (k

Ω)

1

215.8

687.3

1703

3294

2

103.0

327.1

807.8

1588

3

65.40

207.0

509.2

1019

4

46.60

147.0

359.9

735.1

5

35.32

110.9

270.3

564.5

6

27.80

27.80

210.6

450.7

7

22.43

22.43

167.9

369.5

8

18.40

18.40

135.9

308.5

9

15.27

15.27

111.0

261.1

10

12.76

12.76

91.16

223.2

11

10.71

10.71

74.87

192.2

12

9.00

9.00

61.30

166.3

13

7.55

7.55

49.82

144.5

14

6.31

6.31

39.97

125.7

15

5.24

5.24

31.44

109.5

16

4.30

4.30

23.97

95.28

17

3.47

3.47

17.39

82.73

18

2.73

2.73

11.53

71.58

19

2.07

2.07

6.298

61.60

20

1.48

1.48

1.583

52.62

Input Fusing and Safety Considerations

The RDF50 series converters have no internal fuse. In order to achieve maximum safety and system protection, always use an input line fuse. We

recommended a 30 A fast acting fuse. It is recommended that the circuit has a transient voltage suppressor diode (TVS) across the input terminals

to protect the unit against surge or spike voltages

and input reverse voltage (as shown). A suitable

part would be 1.5KE180A.

Output Voltage Adjustment

The Trim input permits the user to adjust the

output voltage up by 10% or down by 20%. This

is accomplished by connecting an external

resistor between the Trim pin and either the

+Sense pin or the -Sense pin.

To Trim Down

Connecting an external resistor (Rd) between the Trim pin and the

Vout (+) (or +Sense) pin decreases the output voltage. The following

table can be used to determine the required external resistor value to

obtain a percentage output voltage change of Δ%.

TVS

V

On/Off

-Vin

+Vin

1

2

+Vout

+Sense

Trim

-Sense

-Vout

8

7

6

5

4

3

Vin

+

-

Load

Trim down Rd

Trim up Ru

To Trim Up

Connecting an external resistor (Ru) between the Trim pin and the

Vout (-) (or -Sense) pin increases the output voltage. The following

table can be used to determine the required external resistor value to

obtain a percentage output voltage change of Δ%.