82 Application Programs
Application 4. Providing Time-Varying Voltages
Overview of Application
To burn-in devices using thermal or mechanical cycling/stress, cyclical time-varying voltage is provided by programming a
set of voltage and dwell time points that repetitively sequence over time.
For this example, the power module must provide the repetitive waveform shown in Figure B4-1. This time-varying voltage
will be applied to a hybrid IC. By continually cycling the voltage from 0 to 7 volts over a 33 second interval, the hybrid is
given time to heat up and undergo thermal and mechanical stress as the welds inside the hybrid expand and contract, and
then subsequently cool down.
Figure B4-1. Voltage Waveform for Application #4
In addition to generating the cyclical voltage, it is desirable to have the power module notify the computer should the device
fail and stop the cycling. Since the module is monitoring test status, the computer is free to perform other tests.
The MPS can address this application using dwell-paced repetitive Lists. This application could be thought of as a simple
power arbitrary waveform generator. To get the desired time-varying voltage, you must be able to describe the waveform in
20 discrete voltage points, with each point ranging from 10 ms to 65 seconds. This range of dwell times determines the
range of frequencies (or time rate of change) of the voltage waveform to be generated.
Once the waveform has been described, it is downloaded to the module. Upon being triggered, it will repetitively generate
the waveform without computer intervention.
The module will also be set up to generate an SRQ and stop the voltage cycling of the hybrid should fail. If the hybrid fails
by shorting, the module will go into CC. This change in status will cause the module to protect the DUT by disabling the
output, which will stop the test and generate an SRQ. (Open circuit failures will not be detected. Since failures of this type
are less likely to have destructive consequences, detection is not required.)