7. OUTPUT TRIMMING

(OPTIONAL)

The output voltages are preset to nominal values as indicated by the models table at the factory. If desired, the output voltage may

optionally be trimmed to a different value (+/- 10%) with external resistors and/or potentiometer as shown below.

To trim the output voltage with fixed resistors, the output voltage can be calculated as follows.

Trim-Up

Trim-Down

FIGURE 4: TRIM-UP VOLTAGE SETUP

FIGURE 5: TRIM-DOWN VOLTAGE SETUP

The value of R

The value of R

Where: R

Where: R

the nominal output voltage. Vo is the desired output voltage.

the nominal output voltage. Vo is the desired output voltage.

R1 and R2 are internal to the unit and are defined in Table 1.

R1 and R2 are internal to the unit and are defined in Table 2.

For example, to trim-up the output voltage of 5.0V module

For example, to trim-down the output voltage of 5.0V module

(VHB150W-Q48-S5) by 8% to 5.4V, R

(VHB150W-Q48-S5) by 8% to 4.6V, R

as follows:

as follows:

page

date

DESCRIPTION: half-brick dc-dc converter

6 of 9

08/2009

20050

phone

phone 503.612.2300 fax

www.v-infinity.com

fax 503.612.2383

PART NUMBER: VHB150W

R load

10K

Ω

Trimpot

+Vin

-Vin

-Vo

-S

Trim

+S

+Vo

(

Vo –Vo,nom

)

(k Ω

×

−

=

1

))

(

(R

2

R

Vo

–

Vo,nom

)

(

Vo

–

Vo,nom

)

(k Ω

×

−

=

1

))

(

(R

2

R

Output

Voltage(V)

R1

(Kohm)

R2

(Kohm)

3.3V

3.168

7.2

5V

5.8

3.3

12V

18.945

4.636

15V

25.189

7.191

24V

41.442

6.977

Table 1

R load

R trim-up

+Vin

-Vin

+Vo

+S

Trim

-S

-Vo

R load

R trim-down

+Vin

-Vin

+Vo

+S

Trim

-S

-Vo

5

–

5.4

)

(

5

–

5.4

9.18kΩ

×

−

=

))

(

(5.8 3.3

Vo – Vo,nom = 5.4 – 5.0 = 0.4V

= 5.8 kΩ

= 3.3 kΩ

2

R

1

R

=

Vo,nom – Vo = 5.0 – 4.6 = 0.4V

= 5.8 kΩ

= 5.32 kΩ

2

R

1

R

4.6

–

5

)

(

4.6

–

5

11.2kΩ

×

−

=

=

))

(

(5.8 5.32

FIGURE 3. TRIMMING WITH

EXTERNAL POTENTIOMETER

Output

Voltage(V)

R1

(Kohm)

R2

(Kohm)

3.3V

6.18

15

5V

5.8

5.62

12V

86.45

60.1

15V

150

68

24V

430

120

Table 2

(

Vo –Vo,nom

)

(k Ω

×

−

=

1

))

(

(R

2

R

Vo

–

Vo,nom

)

(

Vo

–

Vo,nom

)

(k Ω

×

−

=

1

))

(

(R

2

R