24V Input

24V Micro Family

Rev 5.3

vicorpower.com

Page 11 of 14

4/2013

800 735.6200

Parallel Operation

The PR pin supports paralleling for increased power with N+1

(N+M) redundancy. Modules of the same input voltage, output

voltage, and power level will current share if all PR pins are

suitably interfaced.

Compatible interface architectures include the following:

AC coupled single-wire interface.

All PR pins are connected

µF (500 V)

capacitors. This interface supports current sharing and is fault

tolerant except for the communication bus. Up to three

converters may be paralleled by this method. See Figure 9.

Transformer coupled interface.

For paralleling four or more

converters a transformer coupled interface is required. See

Figure 10.

For details on parallel operation please refer to the

Design Guide & Applications Manual for Maxi, Mini, Micro Family.

Figure9—ACcoupledsingle-wireinterface.

* See Maxi, Mini, Micro Design Guide.

+IN

PC

PR

–IN

+IN

PC

PR

–IN

Module2

Module1

+

Parallel

Bus

–

0.2 µF

0.001 µF

0.2 µF

0.001 µF

Lowinductance

groundplane

orbus

4.7 nF

4.7 nF

4.7 nF

4.7 nF

Z1

*

Z1

*

+IN

PC

PR

–IN

+IN

PC

PR

–IN

Module2

Module1

T1

T2

+

–

0.2 µF

0.2 µF

Parallel

Bus

4.7 nF

4.7 nF

4.7 nF

4.7 nF

Z1

*

Z1

*

Figure10—Transformer-coupledinterface.

PARALLEL BUS - PR PIN

Output Voltage Programming

The output voltage of the converter can be adjusted or

programmed via fixed resistors, potentiometers or voltage

DACs. See Figure 8.

Figure8—Outputvoltagetrimdownandtrimupcircuit.

Load

Trim Down

Error

Amp

1 k

Ω

1.23 V

0.033

μF

+OUT

SC

–OUT

1,000 Vout

Vnom – Vout

1,000 (Vout –1.23) Vnom

1.23 (Vout – Vnom)

– 1,000

Trim Up

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 between the SC

and pins. Do not bypass the SC pin directly with a

capacitor.

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 between the SC

and pins. Do not bypass the SC pin directly with a

capacitor.

3. Do not trim the converter above maximum trim range

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

circuitry may be activated.

SECONDARY CONTROL - SC PIN

Trim resistor values calculated automatically:

On-line calculators for trim resistor values are available on the

vicor website at:

asp.vicorpower.com/calculators/calculators.asp?calc=1

Resistor values can be calculated for fixed trim up, fixed trim

down and for variable trim up or down.