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dc1994afa

DEMO MANUAL DC1994A

Quick start proceDure

Demonstrationcircuit1994iseasytosetuptoevaluatethe

performanceoftheLT3752/LT8311chipset.RefertoFigure1

for proper measurement equipment setup and follow the

procedure below:

NOTE.Whenmeasuringtheoutputvoltageripple,caremust

be taken to avoid a long ground lead on the oscilloscope

probe. Measure the output voltage ripple by touching the

probe tip and ground ring directly across the last output

capacitor as shown in Figure 1.

1. Set an input power supply that is capable of 18V to 72V

to 18V. Then turn off the supply.

2. Directanairflowof200LFMacrosstheunitforsustained

operation at full load.

3. Withpoweroff,connectthesupplytotheinputterminals

a. Inputvoltageslowerthan18Vcankeeptheconverter

from turning on due to the undervoltage lockout

feature of the LT3752/LT8311.

b. If efficiency measurements are desired, an ammeter

capableofmeasuring10ADCcanbeputinserieswith

the input supply in order to measure the DC1994A’s

input current.

c. A voltmeter with a capability of measuring at least

72Vcanbeplacedacrosstheinputterminalsinorder

to get an accurate input voltage measurement.

4. Turn on the power at the input.

NOTE. Make sure that the input voltage does not exceed

100V.

5. Check for the proper output voltage of 12V. Turn off

the power at the input.

6. Once the proper output voltages are established, con-

nect a variable load capable of sinking 12A at 12V to

for 0A.

a. If efficiency measurements are desired, an ammeter

or a resistor shunt that is capable of handling 12ADC

can be put in series with the output load in order to

measure the DC1994A’s output current.

b. A voltmeter with a capability of measuring at least

12V can be placed across the output terminals in

ordertogetanaccurateoutputvoltagemeasurement.

7. Turn on the power at the input.

NOTE. If there is no output, temporarily disconnect the

load to make sure that the load is not set too high.

8. Once the proper output voltage is again established,

adjust the load within the operating range and observe

the output voltage regulation, ripple voltage, efficiency

and other desired parameters.