Datasheet
rev.
page
date
DESCRIPTION: dc-dc converter
4 of 6
05/2009
20050 SW 112
th
Ave. Tualatin, Oregon 97062 phonephone 503.612.2300 faxfax 503.612.2382
PART NUMBER: VHB75
2. 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 3: TRIM-UP VOLTAGE SETUP FIGURE 4: TRIM-DOWN VOLTAGE SETUP
The value of R
trim-up
is defined as: The value of R
trim-down
is defined as:
Where: R
trim-up
is the external resistor in K
Ω
. V
o,nom
is the Where: R
trim-down
is the external resistor in K
Ω
. V
o,nom
is the
nominal output voltage. V
o
is the desired output voltage. nominal output voltage. V
o
is the desired output voltage.
R
1
and R
2
are internal to the unit and are defined in R
1
andR
2
are internal to the unit and are defined in
Table 1. For example, to trim-up the output voltage of 5.0V Table 2. For example, to trim-up the output voltage of 5.0V
module (VHB75-Q48-S5) by 8% to 5.4V, R
trim-up
is calculated module (VHB75-Q48-S5) by 8% to 4.6V, R
trim-down
is calculated
as follows: as follows:
R load
10KΩ
Trimpot
+Vin
-Vin
-Vo
-S
Trim
+S
+Vo
FIGURE 2. TRIMMING WITH
EXTERNAL POTENTIOMETER
16.923
14.76
13.304
8.25
7.2
8.25
ΩΩ
42.215
25.474
19.656
5.8
3.168
2.877
24V
15V
12V
5V
3.3V
2.5V
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
R2 = 8.25 KΩ
R1 = 5.8 KΩ
o o, nom = 5.4 - 5.0 = 0.4 V
V - V
=
= 6.25 (KΩ)
R
0.4
trim-up
5.8 - 8.25 x 0.4
V - V
=
= 3.93 (KΩ)
R
0.4
trim-down
5.8 - 10.57 x 0.4
R2 = 10.57 KΩ
R1 = 5.8 KΩ
oo, nom = 5.0 - 4.6 = 0.4 V
=
(KΩ)
R
o o, nom
V - V
o o, nom
trim-up
R1 - R2 x (V - V )
=
(KΩ)
R
oo, nom
V - V
oo, nom
trim-down
R1 - R2 x (V - V )
130
94
60.1
10.57
15
10.57
ΩΩ
430
150
86.45
5.8
6.18
2.923
24V
15V
12V
5V
3.3V
2.5V
Table 2
For more information, please visit the product page.