6.6.1 Creating Scalar Aliases
Some scalar measurements are made automatically after each DVM simulation test. In many cases, the names for these scalars are determined by the probes on the schematic, which means that the names are the same for every test. For example, when a Bode plot test objective runs, the following scalars are generated for each test:
- gain_margin
- phase_margin
- gain_crossover_frequency
Comparing one set of scalar measurements with the same results from another simulation test that runs under different operating conditions is difficult since all scalar-measurement names are the same. To make this comparison possible, you can use the Alias() function to rename the scalars from each set of tests to reflect the distinguishing test conditions. This becomes even more important when generating curves from the scalar measurements as you will see in 6.6.5 Using the CreateXYScalarPlot Function.
To set up aliases for scalar measurements, follow this steps:
- Open the testplan from SIMPLIS_dvm_tutorial_examples.zip at this path: testplans/6.3_jumpers.testplan.
- Insert three columns between Jumper and S ource.
- Add Create in the header row for each of the three new columns.
- In the Create columns in the first set of tests, add the following three Alias()
functions in each row for the nominal output voltage tests:
- Alias(gain_margin,gain_margin_nom)
- Alias(phase_margin,phase_margin_nom)
- Alias(gain_crossover_freq,gain_crossover_freq_nom)
- In the Create columns in the second set of tests, add these three
Alias() functions in each row for the 600mV output voltage
tests:
- Alias(gain_margin,gain_margin_600mV)
- Alias(phase_margin,phase_margin_600mV)
- Alias(gain_crossover_freq,gain_crossover_freq_600mV)
Result: When you run the testplan, each entry creates a new scalar name with the same scalar value as the original and retains the original scalar name and its value in the test report. The Alias() function copies the value to the new scalar name.
The modified alias testplan should now like the following with the added entries shown in red. The testplan is available from SIMPLIS_dvm_tutorial_examples.zip at this path: testplans/6.6.1_alias.testplan.
| *** | ||||||||
|---|---|---|---|---|---|---|---|---|
| *** 6.6.1_alias.testplan: alias testplan for DVM tutorial section 6.6.1 | ||||||||
| *** | ||||||||
| *?@ Analysis | Objective | Jumper | Create | Create | Create | Source | Load | Label |
| *** | ||||||||
| Ac | BodePlot(OUTPUT:1) | Close(J1) | Alias(gain_margin,gain_margin_nom) | Alias(phase_margin,phase_margin_nom) | Alias(gain_crossover_freq,gain_crossover_freq_nom) | Source(INPUT:1, Nominal) | Load(OUTPUT:1, Light) | VOUT=1.505V|Bode Plot|Vin Nominal|Light Load |
| Ac | BodePlot(OUTPUT:1) | Close(J1) | Alias(gain_margin,gain_margin_nom) | Alias(phase_margin,phase_margin_nom) | Alias(gain_crossover_freq,gain_crossover_freq_nom) | Source(INPUT:1, Nominal) | Load(OUTPUT:1, 50%) | VOUT=1.505V|Bode Plot|Vin Nominal|90% Load |
| Ac | BodePlot(OUTPUT:1) | Close(J1) | Alias(gain_margin,gain_margin_nom) | Alias(phase_margin,phase_margin_nom) | Alias(gain_crossover_freq,gain_crossover_freq_nom) | Source(INPUT:1, Nominal) | Load(OUTPUT:1, 100%) | VOUT=1.505V|Bode Plot|Vin Nominal|100% Load |
| *** | ||||||||
| *** the jumper position sets the output voltage to 0.6V | ||||||||
| *** | ||||||||
| Ac | BodePlot(OUTPUT:1) | Open(J1) | Alias(gain_margin,gain_margin_600mV) | Alias(phase_margin,phase_margin_600mV) | Alias(gain_crossover_freq,gain_crossover_freq_600mV) | Source(INPUT:1, Maximum) | Load(OUTPUT:1, Light) | VOUT=0.6V|Bode Plot|Vin Maximum|Light Load |
| Ac | BodePlot(OUTPUT:1) | Open(J1) | Alias(gain_margin,gain_margin_600mV) | Alias(phase_margin,phase_margin_600mV) | Alias(gain_crossover_freq,gain_crossover_freq_600mV) | Source(INPUT:1, Maximum) | Load(OUTPUT:1, 50%) | VOUT=0.6V|Bode Plot|Vin Maximum|50% Load |
| Ac | BodePlot(OUTPUT:1) | Open(J1) | Alias(gain_margin,gain_margin_600mV) | Alias(phase_margin,phase_margin_600mV) | Alias(gain_crossover_freq,gain_crossover_freq_600mV) | Source(INPUT:1, Maximum) | Load(OUTPUT:1, 100%) | VOUT=0.6V|Bode Plot|Vin Maximum|100% Load |
When this testplan is run on the schematic from 6.3 Using Jumpers (available from SIMPLIS_dvm_tutorial_examples.zip at this path:
LTC3406B/6.3_LTC3406B - DVM ADVANCED.sxsch
), the new scalar names are in the test report shown below and outlined in red.
Some auto-generated scalars are reformatted when presented in the html version of the report. Currently this is limited to the table of values with entries for the AVG, MIN, MAX, RMS and Pk2Pk values.
The actual scalar names that you need to use in the Alias() function for these scalars are
- Avg(scalar_name)
- Min(scalar_name)
- Max(scalar_name)
- Rms(scalar_name)
- Pk2Pk(scalar_name)
where scalar_name is the name of the scalar in the test report. For example, if you want to alias the average nominal output voltage in the report above, you need to add an another create column with an entry such as Alias(Avg(VOUT,avg_vout_nom).