DVM - Design Verification Module

Startup() Test Objective

The purpose of the Startup() test is to determine the converter response to a startup. The input is configured as a Ramped Input Source with the starting voltage set to 0V. The output is configured as a   resistive output load. The final voltage as an argument to the Startup() function, DVM also disables all initial conditions on the schematic before starting the simulation. For information about how to change this behavior, see the PRESERVE_IC optional parameter.

A transient simulation is used in the Startup() test with the initial value of 0V. The timing for both the ramp input source and the transient simulation is determined by the values entered in the Startup Tab of the Full Power Assist DVM control symbol, which is shown below.

The test report  includes source, load, and frequency graphs as well as the following scalar values which are defined in the Measured Scalar Values section below:

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Testplan Syntax

The Startup() function has the following syntax with the arguments described in the table below:

Startup(REF, FINAL_VOLTAGE)
Startup(REF, FINAL_VOLTAGE, OPTIONAL_PARAMETER_STRING)  

Argument Range Description

REF

n/a

The actual reference designator of the DVM Source or the generic syntax of INPUT:n where n is an integer indicating a position in the list of managed DVM sources. 

FINAL_VOLTAGE

 

The final source voltage

OPTIONAL_PARAMETER_STRING

n/a

Parameter string with a combination of one or more timing parameters:

  • PRESERVE_IC*
  • TIME_DELAY*
  • RISE_TIME*
  • CYCLES_TO_RECOVER*

*    If more than one parameter is specified, join the parameter key-value pairs with a space, as shown in the optional parameter string section below.

The PRESERVE_IC parameter is unique to the Startup() test objective. If this parameter value is equal to the string TRUE, DVM will not clear the initial conditions from the circuit under test before the simulation starts. This allows you to use a specific set of initial conditions for the design.

Simulation Timing

DVM sets the timing parameters for the Startup() test objective based on values that you enter on the following two tabs in the DVM  Full Power Assist control symbol:

The time delay, rise time, and the simulation stop time are determined by these calculations:

\[ \text{TIME_DELAY} = \frac{\text{CYCLES_BEFORE_EVENT}}{\text{SWITCHING_FREQUENCY}} \]

\[ \text{RISE_TIME} = \frac{\text{FINAL_VOLTAGE}}{\text{SLEW_RATE}}\]

 DVM then calculates the simulation stop time as follows:
\[ \text{STOP_TIME} = \text{TIME_DELAY} + \text{RISE_TIME} + \frac{\text{CYCLES_TO_RECOVER}}{\text{SWITCHING_FREQUENCY}}\]

Note: The switching frequency and cycles to recover parameters are not the actual measured values from a simulation; they are constant values taken from the DVM control symbol. Also, you can override time delay, rise time, and cycles to recover on a test-by-test basis by using the optional parameter string.

The input voltage ramp/step timing is annotated on the graph below:

Annotation Value
X0 TIME_DELAY
X1 TIME_DELAY + RISE_TIME
Y0

0
Y1

FINAL_VOLTAGE

Source and Load Subcircuit Configuration

The Startup() test objective sets the source and load subcircuits to the following:

Source Load

Ramp Input Source

Resistive Load

Loads other than the output under test are set to the Resistive Load. All other sources are set to the DC Input Source.

Measured Scalar Values

The Startup() test objective measures the following scalar values:

Scalar Name

Description

sw_freq

 A number which represents the converter switching frequency

vout{n}_recovery_time

The number {n} in the scalar name is an integer indicating a position in the list of managed DVM loads. The three possible return values are the following:

  • A number which represents the time the converter took to adjust the output voltage to within the regulation tolerance set in the Output tab of the Full Power Assist control symbol.
  • The value "never left regulation" is returned if the output under test never left the regulation window.

  • The value "left regulation and never recovered" is returned if the output under test leaves the regulation window and does not recover before the end of the simulation.

Measured Specification Values

In the following table, {load_name} is the name assigned to each load. The default value is LOAD. DVM forces each load name to be unique so that the scalar and specification values for each load are unique.

Scalar Name

PASS/FAIL Criteria

Min_V{load_name}

The minimum value of the output voltage during the simulation time is greater that the minimum specification value.

Max_V{load_name}

The maximum value of the output during the simulation time is less than the maximum specification value.

Max_V{load_name}_overshoot

The maximum value of the output during the simulation time is less than the maximum overshoot specification value.

Testplan Example

The Startup() test objective is used in several built-in testplans. Shown below is a startup test from the Syncbuck_1in_1out testplan. This test configures the source to ramp to the Maximum symbolic value. This Maximum symbolic value is defined on the Input tab of the Full Power Assist DVM control symbol.

*?@ Analysis Objective Source Load Label
Transient Startup(INPUT:1, Maximum)   Load(OUTPUT:1, 50%) Transient|Startup|50% Load|0V to Vin Maximum

Optional Parameter String

The following Startup() test objective uses the OPTIONAL_PARAMETER_STRING argument to set the final voltage to the Maximum symbolic value, the time delay to 25us and the rise time to 100us.

Startup(INPUT:1, Maximum, TIME_DELAY=25u RISE_TIME=100u)

Test Report

You can view the complete test report in a new browser window here: Startup() Test Report. Below is an interactive link to the same test report.

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