LT3757 datasheet(11/24 Pages) AD

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LT8300

Rev. A

For more information www.analog.com

APPLICATIONS INFORMATION

In general, choose a transformer with its primary mag-

netizing inductance about 20% to 40% 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 LT8300. 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.

Linear Technology has worked with several leading mag-

netic component manufacturers to produce pre-designed

flyback transformers for use with the LT8300. 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., 4:1, 2:1,

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

mutual inductance.

Table 5. Predesigned Transformers — Typical Specifications

TRANSFORMER

PART NUMBER

LPRI

(µH)

LLEAKAGE

(µH)

NP:NS:NB

VENDOR

TARGET APPLICATIONS

750312367

400

4.5

8:1

Wurth Elektronik

48V to 3.3V/0.51A, 24V to 3.3V/0.37A, 12V to 3.3V/0.24A

750312557

300

2.5

6:1

Wurth Elektronik

48V to 3.3V/0.42A, 24V to 3.3V/0.32A, 12V to 3.3V/0.22A

48V to 5V/0.38A, 24V to 5V/0.27A, 12V to 5V/0.17A

750312365

300

1.8

4:1

Wurth Elektronik

48V to 5V/0.29A, 24V to 5V/0.22A, 12V to 5V/0.15A

750312558

300

1.75

2:1:1

Wurth Elektronik

48V to ±12V/67mA, 24V to ±12V/50mA, 12V to ±12V/33mA

48V to ±15V/62mA, 24V to ±15V/44mA, 12V to ±15V/28mA

750312559

300

1:1

Wurth Elektronik

48V to 24V/67mA, 24V to 24V/50mA, 12V to 24V/33mA

750311019

400

6:1:2

Wurth Elektronik

48V to 3.3V/0.42A, 24V to 3.3V/0.32A, 12V to 3.3V/0.22A

48V to 5V/0.38A, 24V to 5V/0.27A, 12V to 5V/0.17A

750311558

300

1.5

4:1:1

Wurth Elektronik

48V to 5V/0.29A, 24V to 5V/0.22A, 12V to 5V/0.15A

750311660

350

2:1:0.33

Wurth Elektronik

48V to 12V/0.134A, 24V to 12V/0.1A, 12V to 12V/0.066A

48V to 15V/0.124A, 24V to 15V/0.088A, 12V to 15V/0.056A

750311838

350

2:1:1

Wurth Elektronik

48V to ±12V/67mA, 24V to ±12V/50mA, 12V to ±12V/33mA

48V to ±15V/62mA, 24V to ±15V/44mA, 12V to ±15V/28mA

750311659

300

1:1:0.2

Wurth Elektronik

48V to 24V/67mA, 24V to 24V/50mA, 12V to 24V/33mA

10396-T026

300

2.5

6:1:2

Sumida

48V to 3.3V/0.42A, 24V to 3.3V/0.32A, 12V to 3.3V/0.22A

48V to 5V/0.38A, 24V to 5V/0.27A, 12V to 5V/0.17A

10396-T024

300

4:1:1

Sumida

48V to 5V/0.29A, 24V to 5V/0.22A, 12V to 5V/0.15A

10396-T022

300

2:1:0.33

Sumida

48V to 12V/0.134A, 24V to 12V/0.1A, 12V to 12V/0.066A

48V to 15V/0.124A, 24V to 15V/0.088A, 12V to 15V/0.056A

10396-T028

300

2.5

2:1:1

Sumida

48V to ±12V/67mA, 24V to ±12V/50mA, 12V to ±12V/33mA

48V to ±15V/62mA, 24V to ±15V/44mA, 12V to ±15V/28mA

L10-0116

500

7.3

6:1

BH Electronics

48V to 3.3V/0.42A, 24V to 3.3V/0.32A, 12V to 3.3V/0.22A

48V to 5V/0.38A, 24V to 5V/0.27A, 12V to 5V/0.17A

L10-0112

230

3.38

4:1

BH Electronics

48V to 5V/0.29A, 24V to 5V/0.22A, 12V to 5V/0.15A

L11-0067

230

2.16

4:1

BH Electronics

48V to 5V/0.29A, 24V to 5V/0.22A, 12V to 5V/0.15A

* All the transformers are rated for 1.5kV Isolation.

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