DC/DC Converter

URF_LP-20WR3 Series

2015.08.12-A/2

Page 4 of 6

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Vin

GND

+Vo

0V

DC

Cin

DC

Cout

Fig. 2

Vin(VDC)

Cout(µF)

Cin(µF)

3.3/5

470

100

9/12/15

220

24

100

2. EMC solution-recommended circuit

LDM1

②

C0

MOV

FUSE

①

C1

V in

GND

+

Vin

GND

+Vo

0V

DC/DC

CY1

CY2

C3

LOAD

C2

Fig. 3

Notes: Part ① in the Fig. 3 is used for EMS test and part ② for EMI filtering;

selected based on needs.

Parameter description

Model

Vin:24V

Vin:48V

FUSE

Choose according to actual input current

MOV

S14K35

S14K60

C0

330µF/50V

330µF/100V

C1/C2

1µF/50V

1µF/100V

C3

Refer to the Cout in Fig.2

LDM1

6.8mH

CY1

1nF/3KV

CY2

1nF/3KV

EMC solution-recommended circuit PCB layout

Fig. 4

Note: the min. distance of the bonding pads between input & output isolation capacitors (CY1/CY2) shall be ≥ 2mm.

3. Application of Trim and calculation of Trim resistance

0V

Trim

+Vot

0V

Trim

+Vot

Trim up

Trim down

Applied circuits of Trim (Part in broken line is the interior of models)

Calculation formula of Trim resistance:

up:

a=

Vref

Vo’-Vref

R =

T

R -a

2

down:

a=

Vref

Vo’-Vref

R =

T

R -a

1

a is a self-defined parameter, with

no real meaning.

Vout(V)

R1(KΩ)

R2(KΩ)

R3(KΩ)

Vref(V)

3.3

4.801

2.87

12.4

1.25

5

2.883

2.87

10

2.5

9

7.500

2.87

15

2.5

12

11.000

2.87

15

2.5

15

14.494

2.87

15

2.5

24

24.872

2.87

17.8

2.5