LT8301 datasheet(11/24 Pages) AD

11 / 24 page

LT8301

Rev. B

For more information www.analog.com

APPLICATIONS INFORMATION

In general, choose a transformer with its primary mag-

netizing inductance about 30% larger than the minimum

values calculated above. A transformer with much larger

inductance will have a bigger physical size and may cause

instability at light load.

Selecting a Transformer

Transformer specification and design is perhaps the most

critical part of successfully applying the LT8301. In addi-

tion to the usual list of guidelines dealing with high fre-

quency isolated power supply transformer design, the

following information should be carefully considered.

Analog Devices has worked with several leading magnetic

component manufacturers to produce pre-designed fly-

back transformers for use with the LT8301. Table 1 shows

the details of these transformers.

Turns Ratio

Note that when choosing the RFB resistor to set output

voltage, the user has relative freedom in selecting a trans-

former turns ratio to suit a given application. In contrast,

the use of simple ratios of small integers, e.g., 3:1, 2:1,

1:1, provides more freedom in settling total turns and

mutual inductance.

Table 1. Predesigned Transformers—Typical Specifications

TRANSFORMER

PART NUMBER

DIMENSIONS

× L × H) (mm)

LPRI

(µH)

LLKG

(µH)

NP:NS

RPRI

(mΩ)

RSEC

(mΩ)

VENDOR

TARGET APPLICATIONS

VIN (V)

VOUT (V)

IOUT (A)

750313973

15.24

× 13.34 × 11.43

4:1

Würth Electronik

8 to 36

3.3

0.80

750370047

13.35

× 10.8 × 9.14

3:1:1

12.5

Würth Electronik

8 to 32

0.55

750313974

15.24

× 13.34 × 11.43

3:1

Würth Electronik

8 to 36

0.55

750313970

15.24

× 13.34 × 11.43

2:1

Würth Electronik

18 to 42

3.3

0.75

750310799

9.14

× 9.78 × 10.54

0.125

1:1:0.33

Würth Electronik

8 to 30

0.22

750313972

15.24

× 13.34 × 11.43

1:1

185

Würth Electronik

18 to 42

0.42

750313975

15.24

× 13.34 × 11.43

1:2

110

865

Würth Electronik

8 to 36

0.12

750313976

15.24

× 13.34 × 11.43

1:4

110

2300

Würth Electronik

8 to 32

0.05

12387-T036

15.5

× 12.5 × 11.5

4:1

160

Sumida

8 to 36

3.3

0.80

12387-T037

15.5

× 12.5 × 11.5

3:1

210

Sumida

8 to 36

0.55

12387-T040

15.5

× 12.5 × 11.5

1.5

2:1

210

Sumida

18 to 42

3.3

0.75

12387-T041

15.5

× 12.5 × 11.5

1.5

1:1

210

200

Sumida

18 to 42

0.42

12387-T038

15.5

× 12.5 × 11.5

1:2

220

460

Sumida

8 to 36

0.12

12387-T039

15.5

× 12.5 × 11.5

1:4

220

2200

Sumida

8 to 32

0.05

PA3948.003NL

15.24

× 13.08 × 11.45

1.45

4:1

210

Pulse Engineering

8 to 36

3.3

0.80

PA3948.004NL

15.24

× 13.08 × 11.45

1.95

3:1

220

Pulse Engineering

8 to 36

0.55

PA3948.001NL

15.24

× 13.08 × 11.45

1.45

2:1

410

Pulse Engineering

18 to 42

3.3

0.75

PA3948.002NL

15.24

× 13.08 × 11.45

1.45

1:1

405

235

Pulse Engineering

18 to 42

0.42

PA3948.005NL

15.24

× 13.08 × 11.45

1.60

1:2

220

1275

Pulse Engineering

8 to 36

0.12

PA3948.006NL

15.24

× 13.08 × 11.45

1.65

1:4

220

3350

Pulse Engineering

8 to 32

0.05

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