5V to 3.3V Buck Converter With 5V Output

This circuit minimizes both board space and cost by eliminating a

second regulator.

VERSA-PAC’s gap serves to prevent core

saturation during the switch on-time and also stores energy for the

+5V load which is delivered during the flyback interval. The +3.3V

buck winding is configured by placing two windings in series while

the +5V is generated by an additional flyback winding stacked on

the 3.3V output. Extra windings are paralleled with primary

windings to handle more current. The turns ratio of 2:1 adds 1.67V

to the +3.3V during the flyback interval to achieve +5V.

+V

+5V@

1A

+3.3V@

4.2A

+

+3.3V@

12.5A

+3.3V@

6A

RTN

+V

RTN

VERSA-PAC

VP5-0083

VERSA-PAC

VP5-0083

VERSA-PAC

VP5-0083

12

11

10

9

8

7

1

12 11 10

12 3

987

45

+

+

+

6

2

3

4

5

6

LEVEL SHIFT

12,11

1,2

7

6

10,9,8

3,4,5

Synchronous

Controller

IC

Synchronous

Controller

IC

Controller

IC

W/Integral

Switch

+

+

+V

+5V@

1A

+3.3V@

4.2A

+

+3.3V@

12.5A

+3.3V@

6A

RTN

+V

RTN

VERSA-PAC

VP5-0083

VERSA-PAC

VP5-0083

VERSA-PAC

VP5-0083

12

11

10

9

8

7

1

12 11 10

12 3

987

45

+

+

+

6

2

3

4

5

6

LEVEL SHIFT

12,11

1,2

7

6

10,9,8

3,4,5

Synchronous

Controller

IC

Synchronous

Controller

IC

Controller

IC

W/Integral

Switch

+

+

3.3V Buck Converter

This circuit utilizes the gap of the VP5-0083 to handle the 12.5

Amp output current without saturating. In each of the five

VERSA-

PAC sizes, the gap is varied to achieve a selection of specific

inductance and current values (see

VERSA-PAC Data Table).

All six windings are connected in parallel to minimize AC/DC

copper losses and to maximize heat dissipation. With

VERSA-

PAC, this circuit works well at or above 300 KHz. Also, the closed

flux-path EFD geometry enables much lower radiation

characteristics than open-path bobbin core style components.

LITHIUM-ION BATTERY TO 3.3V SEPIC CONVERTER

The voltage of a Lithium-Ion Battery varies above and below

+3.3V depending on the degree of charge. The SEPIC

configuration takes advantage of

VERSA-PAC’s multiple tightly

coupled windings. This results in lower ripple current which lowers

noise and core losses substantially. The circuit does not require a

snubber to control the voltage “spike” associated with switch turn-

off, and is quite efficient due to lower RMS current in the windings.

+V

+5V@

1A

+3.3V@

4.2A

+

+3.3V@

12.5A

+3.3V@

6A

RTN

+V

RTN

VERSA-PAC

VP5-0083

VERSA-PAC

VP5-0083

VERSA-PAC

VP5-0083

12

11

10

9

8

7

1

12 11 10

12 3

987

45

+

+

+

6

2

3

4

5

6

LEVEL SHIFT

12,11

1,2

7

6

10,9,8

3,4,5

Synchronous

Controller

IC

Synchronous

Controller

IC

Controller

IC

W/Integral

Switch

+

+

Unipolar (Flyback)

Power vs Frequency

Maximum Turns

vs American Wire Gauge

Bipolar (Push-Pull)

Power vs Frequency

Frequency, kHz

American Wire Gauge

100

0.0

5.0

10.0

15.0

20.0

25.0

30.0

35.0

40.0

200

300

400

500

VP 5

VP 4

VP 3

VP 2

VP 1

Size 5

Size 4

Size 3

Size 2

Size 1

27

1

10

100

1000

10000

28

29

30

31

32

33

34

35

36

37

38

39

40

41

42

Frequency, kHz

100

0.0

10.0

20.0

30.0

40.0

50.0

60.0

70.0

200

300

400

500

VP 5

VP 4

VP 3

VP 2

VP 1

Unipolar (Flyback)

Power vs Frequency

Maximum Turns

vs American Wire Gauge

Bipolar (Push-Pull)

Power vs Frequency

Frequency, kHz

American Wire Gauge

100

0.0

5.0

10.0

15.0

20.0

25.0

30.0

35.0

40.0

200

300

400

500

VP 5

VP 4

VP 3

VP 2

VP 1

Size 5

Size 4

Size 3

Size 2

Size 1

27

1

10

100

1000

10000

28

29

30

31

32

33

34

35

36

37

38

39

40

41

42

Frequency, kHz

100

0.0

10.0

20.0

30.0

40.0

50.0

60.0

70.0

200

300

400

500

VP 5

VP 4

VP 3

VP 2

VP 1

Bipolar (Push-Pull) Power vs Frequency

Unipolar (Flyback) Power vs Frequency

These curves represent typical power handling capability.

Indicated power levels may not be achievable with all configurations.

®

Inductors and Transformers

(Surface Mount)

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This bulletin is intended to present product design solutions and technical information that will help the end user with design applications. Cooper Electronic

Technologies reserves the right, without notice, to change design or construction of any products and to discontinue or limit distribution of any products. Cooper

Electronic Technologies also reserves the right to change or update, without notice, any technical information contained in this bulletin. Once a product has been

selected, it should be tested by the user in all possible applications.

Life Support Policy: Cooper Electronic Technologies does not authorize the use of any of its products for use in life support devices or systems without the

express written approval of an officer of the Company. Life support systems are devices which support or sustain life, and whose failure to perform, when

properly used in accordance with instructions for use provided in the labeling, can be reasonably expected to result in significant injury to the user.

PM-4301 8/06

© Cooper Electronic

Technologies 2006