90 Application Programs
Application 6. Output Sequencing Paced by the Computer
Overview Of Application
When performing bias supply margin testing, throughput can be maximized by eliminating the command processing time
associated with reprogramming all outputs for each set of limit conditions. Instead, multiple sets of bias limit conditions can
be downloaded to the power modules during test system initialization. During the testing, the computer can use a single
command to simultaneously signal all power modules to step through each test condition.
In this example, the DUT requires + 5 V and ± 12 V. The DUT is tested to ensure proper operation at marginal supply
voltages. The margin specified is ± 5 % of nominal voltage. At each of the combinations given below, the computer first
sets up the three modules and makes a measurement on the DUT. The combinations to be tested are:
Nominal 5 V Nominal + 12 V Nominal - 12 V
4.75 V 12 V -12 V
5 V 12 V -12 V
5.25 V 12 V -12 V
5 V 11.4 V -12 V
5 V 12.6 V -12 V
5 V 12 V - 11.4 V
5 V 12 V - 12.6 V
When conducting this test, the modules will need to be reprogrammed 21 times and seven measurements made. The
command processing time could slow down this test.
The MPS can be used to increase throughput. By downloading all of the combinations into the three modules, each setting
can be quickly stepped through by triggering all modules to change to their next voltage setting and then taking a
measurement from the DUT. This permits testing without command processing overhead.
MPS Features Used
• 20-point voltage List.
• Trigger-paced Lists.
• Trigger in/out from MPS mainframe backplane TTL Trigger.
• Trigger on a GPIB trigger command.
Advantages/Benefits Of The MPS Solution
By using Lists, the module changes its voltage without delays due to processing the command to change the output voltage.
By using triggers, all three outputs can be changed with one command.
The computer loop to change the settings and take a measurement is simplified, because you do not have to explicitly
reprogram each module output. Instead, the loop becomes "Trigger" and "Measure".
Implementation Details
How The MPS Implements The Sequence
The following steps are performed for each point in the List:
The computer sends a trigger command to the first module.
The first module simultaneously sends a backplane TTL Trigger to the other two modules and goes to its next List point.
The second module receives the backplane TTL Trigger and immediately goes to its next List point.
The third module receives the backplane TTL Trigger, immediately goes to its next List point.
The computer gets a measurement from the measurement instrument.