VHB150W Datasheet, PDF (6/9 Pages) CUI INC – half-brick dc-dc converter

PART NUMBER: VHB150W
page 6 of 9
date 08/2009
DESCRIPTION: half-brick dc-dc converter
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.
FIGURE 3. TRIMMING WITH
EXTERNAL POTENTIOMETER
+Vin
-Vin
+Vo
+S
Trim
-S
-Vo
10KΩ
Trimpot
R load
To trim the output voltage with fixed resistors, the output voltage can be calculated as follows.
Trim-Up
Trim-Down
+Vin
+Vo
+Vin
+Vo
+S
=
(R₁−
R₂× (Vo –Vo,nom))
( Vo^T–^rV^imo,nom)
(k Ω)_{R load}
R trim-up
-S
-Vin
-Vo
+S
=
(R_1T−_rimR₂× (Vo,no^Rm^trim–^-dV^owoⁿ))
(Vo,nom –Vo)
R₍l_koad_{Ω )}
-S
-Vin
-Vo
FIGURE 4: TRIM-UP VOLTAGE SETUP
The value of R_trim-up is defined as:
=
(R₁−
R₂× (Vo –Vo,nom))
(Vo –Vo,nom)
(k Ω)
Where: R_trim-up is the external resistor in KΩ. Vo,nom is
the nominal output voltage. Vo is the desired output voltage.
R1 and R2 are internal to the unit and are defined in Table 1.
For example, to trim-up the output voltage of 5.0V module
(VHB150W-Q48-S5) by 8% to 5.4V, R_trim-up is calculated
as follows:
Vo – Vo,nom = 5.4 – 5.0 = 0.4V
R₁ = 5.8 kΩ
R₂ = 3.3 kΩ
=
(5.8−3.3×(5.4 –5))
(5.4– 5)
= 9.18kΩ
FIGURE 5: TRIM-DOWN VOLTAGE SETUP
The value of R_trim-down is defined as:
=
(R₁−
R₂× (Vo,nom – Vo))
(Vo,nom –Vo)
(k Ω)
Where: R_trim-down is the external resistor in KΩ. Vo,nom is
the nominal output voltage. Vo is the desired output voltage.
R1 and R2 are internal to the unit and are defined in Table 2.
For example, to trim-down the output voltage of 5.0V module
(VHB150W-Q48-S5) by 8% to 4.6V, R_trim-down is calculated
as follows:
Vo,nom – Vo = 5.0 – 4.6 = 0.4V
R₁ = 5.8 kΩ
R₂ = 5.32 kΩ
=
(5.8−5.32 ×(5–4.6))
(5– 4.6)
=11.2kΩ
Table 1
Output
Voltage(V)
3.3V
5V
12V
15V
24V
R1
(Kohm)
3.168
5.8
18.945
25.189
41.442
R2
(Kohm)
7.2
3.3
4.636
7.191
6.977
Table 2
Output
Voltage(V)
3.3V
5V
12V
15V
24V
R1
(Kohm)
6.18
5.8
86.45
150
430
R2
(Kohm)
15
5.62
60.1
68
120
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