Vicor Corp. Tel: 800-735-6200, 978-470-2900 Fax: 978-475-6715

V375C3V3C75B DC-DC Converter

Rev. 3

Page 5 of 8

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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.

CONTROL FUNCTIONS - SC PIN

Figure 8—Output voltage trim up circuit.

Figure 7—Output voltage trim down circuit.

1,000 Vout

Vnom - Vout

Trim Up

Load

Error

Amp

1k

Ω

1.23V

0.033

µF

+Out

SC

–Out

Load

Trim Down

Error

Amp

1k

Ω

1.23V

0.033

µF

+Out

SC

–Out

Trim Down

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.

2. The trim down resistor must be connected to the –Out pin.

Trim Up

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.

3. Do not trim the converter above maximum trim range

(typically +10%) or the output over voltage

protection circuitry may be activated.

1,000 (Vout-1.23) Vnom

–1,000

1.23 (Vout-Vnom)

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.