SP48S48-100 Datasheet, PDF (4/7 Pages) Wall Industries,Inc. – 100W DC-DC Converter

WALL INDUSTRIES, INC.
Rev C
APPLICATION NOTES
SP & SPW SERIES
Output Voltage Trim
The following information is provided to allow quick calculation of the trim resistor value for a desired output voltage. The general
procedure for calculating a trim resistor is as follows:
1. Determine the desired output voltage (Vo)
2. Select Equation. (Trim Low/Trim High)
3. Use the data in Table 1 to complete the equation.
4. Evaluate.
In order to trim low use Equation 1 and Table 1 to calculate resistor RTL for the desired output voltage.
Equation 1: Trim Low
RT_L
ª
«
¬
(^VREF
) _RL
V_o  V_REF

(
1
R_H
˜
(V_o
 V_REF
º
))
»
¼

R_LIM
Vo - Desired output voltage.
All resistor values in K ohms.
Schematic 1: Trim Low
In order to trim high use Equation 2 and Table 1 to calculate resistor RTH for the desired output voltage.
Equation 2: Trim High
RT_H
    ^ª
«
V_REF
V_o V_REF
¬« ^{ RH}
V_REF
R_L
º
»
¼»

R _LIM
Vo - Desired output voltage.
All resistor values in K ohms.
Note: Output trim +/- 10% max.
(888) 597-WALL
Schematic 2: Trim High
MODEL
(Output Voltage)
3.3V
R_H
(K OHMS)
0.750
R_LIM
(K OHMS)
0.499
R_L
(K OHMS)
2.32
5.0V
2.49
10.0
2.49
8.0V
5.49
10.0
2.49
9.0V
6.49
10.0
2.49
12.0V
9.53
13.7
2.49
15.0V
12.4
13.7
2.49
24.0V
21.5
15.4
2.49
26.0V
17.6
15.4
1.87
32.0V
23.7
12.7
2.00
Table 1 : Trim Low/High Data Table.
V_REF
(VOLTS)
2.495
2.495
2.495
2.495
2.495
2.495
2.495
2.495
2.495
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