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

375V Maxi Family

Rev. 8.6

Page 11 of 15

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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.

Figure 8 — Output voltage trim up circuit.

Figure 7 — Output voltage trim down circuit.

+OUT

+S

SC

–S

–OUT

Trim Up

Load

Error

Amp

1 k

Ω

1.23 V

0.033

μF

1,000 (Vout –1.23) Vnom

1.23 (Vout – Vnom)

– 1,000

Load

+OUT

+S

SC

–S

–OUT

Trim Down

Error

Amp

1 k

Ω

1.23 V

0.033

μF

1,000 Vout

Vnom – Vout

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 +Sense pin.

3. Do not trim the converter above maximum trim range

(typically +10%) or the output over voltage protection

circuitry may be activated.

CONTROL FUNCTIONS - SC PIN

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 –Sense pin.

Trim resistor values calculated automatically:

On-line calculators for trim resistor values are available

on the vicor website at: vicorpower.com/tools.

Resistor values can be calculated for fixed trim up,

fixed trim down and for variable trim up or down.

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.