0.47µF

C8

127k

R6

10.0k

R10

301k

R7

51.1k

R4

0.082µF

C13

0.01µF

C5

1000pF

C4

6.04K

R8

2.00k

R9

10µF

C11

10µF

C10

TP1

GND

GND

GND

GND

GND

GND

0

R3

1µF

C12

0.1µF

C9

GND

ISOGND

D1

DFLS1100-7

2.0k

R2

10µF

C1

10µF

C2

GND

2200pF

C3

1

2

J3

1

2

J1

1

2

J2

12VOUT

18-32VIN

0

R1

T1

750314597

GND

VOUTISO

VIN

2.2uF

C6

2.2uF

C7

VOUT

1

J4

8VOUT

AGND

1

PGND

2

VIN

3

EN/UVLO

4

RON

5

SS

6

FPWM

7

FB

8

VCC

9

BST

10

SW

11

SW

12

PAD

LM5160DNT

Time = 50 µs/div)

21

LM5160A, LM5160

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SNVSA03C – OCTOBER 2014 – REVISED AUGUST 2016

Product Folder Links: LM5160A LM5160

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With Type 3 Ripple Configuration

8.2.2 LM5160 Isolated Fly-Buck (18-V to 32-V Input, 12-V, 4.5-W Isolated Output)

A typical application example for an isolated Fly-Buck converter operates over an input voltage range of 18 V to

32 V. It provides a stable 12-V isolated output voltage with output power capability of 4.5 W. The complete

schematic of the Fly-Buck application circuit is shown in Figure 28.

Figure 28. 12-V, 4.5-W Fly-Buck Schematic

8.2.2.1 LM5160 Fly-Buck Design Requirements

The LM5160 Fly-Buck application example is designed to operate from a 24-V DC supply with line variations

from 18 V to 32 V. This example provides a space-optimized and efficient 12-V isolated output solution with

secondary load current capability from 0 mA to 400 mA. The primary side remains unloaded in this application.

The switching frequency is set at 300 kHz (nominal). This design achieves greater than 88% peak efficiency.

Table 4. Design Parameters

DESIGN PARAMETER

EXAMPLE VALUE

Input voltage range

18 V - 32 V

Isolated output

12 V

Isolated load current range

0 mA to 400 mA

Nominal switching frequency

300 KHz

Peak Efficiency

88%