CONTROL FUNCTIONS - SC PIN
Output Voltage Programming
The output voltage of the converter can be adjusted or
programmed via fixed resistors, potentiometers or voltage
DACs. See Figures 7 and 8.
+Out
+Out
RU
Trim Up
Error
Amp
Error
Amp
Load
Load
SC
SC
RD
Trim Down
1kΩ
0.033µF
1kΩ
0.033µF
–Out
–Out
1.23V
1.23V
1,000 Vout
1,000 (Vout-1.23) Vnom
1.23 (Vout-Vnom)
R
(ohms) =
D
–
1,000
R
(ohms) =
Vnom - Vout
U
Figure 7—Output voltage trim down circuit.
Figure 8—Output voltage trim up circuit.
Trim Down
Trim Up
1. This converter is not a constant power device – it has a
constant current limit. Hence, available output power is
reduced by the same percentage that output voltage is
trimmed down. Do not exceed maximum rated output current.
1. The converter is rated for a maximum delivered power. To ensure
that maximum rated power is not exceeded, reduce maximum
output current by the same percentage increase in output voltage.
2. The trim up resistor must be connected to the +Out pin.
2. The trim down resistor must be connected to the –Out pin.
3. Do not trim the converter above maximum trim range
(typically +10%) or the output over voltage
protection circuitry may be activated.
Trim resistor values calculated automatically:
On-line calculators for trim resistor values are available
on the vicor website at: vicorpower.com/tools.html.
Resistor values can be calculated for fixed trim up, fixed
trim down and for variable trim up or down cases for both
1st and 2nd Generation DC-DC converters.
In addition to trimming information, the web site and the
Applications Manual also include design tips, applications
circuits, EMC suggestions, thermal design guidelines and
PDF data sheets for all available Vicor products.
Vicor Corp. Tel: 800-735-6200, 978-470-2900 Fax: 978-475-6715
V300C15C150B DC-DC Converter
Rev. 3
Page 5 of 8
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