The PMIC Cranking Profile Test Plugin

Many automotive PMICs are powered by an automotive battery. They are required to regulate output voltage under a variety of conditions at their input rails, particularly those encountered while cranking the engine. Several industry-standard procedures exist for testing these PMICs for cranking profiles. These standards include ISO 16750-2, ISO 7637-2 and CISPR25. Each standard specifies several test pulse profiles. The Cranking Profile Test SIVA plugin has been designed to enable the evaluation and characterization of PMICs when subjected to these profiles.

Test Parameters tab in PMIC Cranking Profile Test Plugin for SIVA

Figure 1. Test Parameters tab in PMIC Cranking Profile Test Plugin for SIVA

 

Figure 1 shows the Test Parameters tab of the Cranking Profile Test plugin in SIVA. The Test Parameters tab has dropdowns and fields that let the test engineer choose the test pulses defined in various standards and sequence them into a composite waveform applied to the DUT. The graphical representation of the pulse and the editable pulse parameters control lets the test engineer tailor the various portions of the test pulse. The Test Parameters tab also contains features that lets the Test engineer build a Test Pulse Set, which he/she can save to a file or open from an already saved file. There are also controls for specifying the repetition characteristics of the pulse sequence.
 

The Cranking Profile Test SIVA plugin offers the following features and advantages:

 

  • Ability to use standard profiles specified by ISO 16750-2, ISO 7637-2 and CISPR25 with configurable timing parameter values that make sense for the standard
  • Ability to generate Arbitrary Voltage Profiles if desired
  • Ability to string together different kinds of Profiles including standard and arbitrary and to specify repetition characteristics.
  • Ability to cycle these profiles over hours or days together
  • Ability to monitor the chosen output voltage rails, input and output currents and any analog or digital test points that may be of interest, Eg. ‘power good’, ‘switching frequency’ or other intermediate test points.
  • Ability to log timestamped waveform traces for these channels with low timing resolution throughout the test if needed. (higher resolution logs covered separately)
  • Ability to control the Device Under Test using a digital protocol using the PXIe-6570 Digital Pattern Instrument and to control timing of the protocol commands to the DUT relative to the Cranking Pulses that are being administered.
  • Ability to synchronize the stimulus waveforms with monitored channel data.
  • Ability to log high-timing-resolution contextual waveform logs just before or after a failure occurs on any combination of the monitored signals
  • Ability to define flexible failure criteria for a selectable list of monitored signals based on either the standard criteria provided (window triggers, edge triggers etc) or using custom LabVIEW logic that the user can specify to the tool in a modular fashion. The context-based high resolution logs will be triggered based on these criteria
  • Ability to configure the load conditions that the cranking profile test will run at.
  • Ability to log the data in a fashion that is DIVE (separately sold tool) compatible so machine learning can assist in recognizing and classifying failures.
General setup for testing automotive PMIC for compliance with cranking profiles specified in ISO 16750-2.

Figure 2. General setup for testing automotive PMIC for compliance with cranking profiles specified in ISO 16750-2.

 

The SIVA plugin for Cranking Profile Reliability Tests requires the following class of instruments with the overriding requirement that the instruments must be PXI instruments. This is because the stimulus, response and logging aspects need to be synchronized in order to align the timing between multiple modules and also properly analyzing the failures in the context of the stimulus. Below are the PXI-based instruments that are needed to use this plugin:
 

Input Power to the PMIC:

 

  • An arbitrary waveform capability is required in order to generate the Cranking Pulses and provide the necessary hardware-timed sequencing of waveforms to supply the SMPS Input voltage rail. If the PMIC input current is 3A or less, many NI PXI SMUs (Source Measure Units) have a sequencing capability that can be employed in order to function as this arbitrary waveform generator and also supply the desired current.
  • If the Input Current is more than 3A or the timing resolution required is finer than the SMUs can provide, then one can use either NI PXI Multifunction IO Module or an NI PXI Arbitrary Waveform Generator Module which provides finer timing resolution. But in this case, one would need to connect the output of the waveform generation instrument chosen to an amplifier which can drive the current needed by the PMIC input rail. Soliton can advise customers on the choice of amplifier based on the specifications of the PMIC.
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    Configuration Settings for the PMIC:

     

    • The Cranking Profile Test Plugin allows uses to set up register write and read to the DUT using popular protocols such as I2C, SPI, PMBUS, SMBUS, SPMI etc. The timing of these commands can be controlled relative to the cranking pulses being generated or the commands can be issued only before and after the test if desired. The register payload being sent and logged from the DUT is also configurable. The equipment of choice for the configuration purpose is the NI PXIe-6570 Digital Pattern Instrument
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      Monitoring Equipment for the PMIC Output and Input Rails and Test Points:

       

      • Low and high timing resolution waveform logs up to a few tens of MS/s can be enabled using PXI MultiFunction IO Modules themselves.
      • For even finer timing resolution, PXI Oscilloscopes may be employed depending on the horizontal and vertical resolution, accuracy, bandwidth and number of channels desired.
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        Electrical Load for the PMIC:

         

        • A 4 quadrant PXI Source Measure Unit (SMU) or (if the load is fixed throughout the test), any non-PXI Remote-programmable Electronic Load in combination with a suitable fixed load such as a decade resistance box should work. The SMU or Electronic Load can also be used for making load voltage and current measurements.
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          The Cranking Profile Test plugin contains a graphical representation of the cranking profiles in its Test Parameters tab. The test engineer can alter various portions of the cranking pulse using the controls. The test engineer can also choose between cold and warm start profiles. These cranking profile parameters can be saved, recalled and edited. Figure 2. Shows the cold and warm star profiles available in the Cranking Profile Test Plugin.

Cranking profiles and their parameters as seen in the Test Parameters tab of the Cranking Profile Test Plugin.

Figure 3. Cranking profiles and their parameters as seen in the Test Parameters tab of the Cranking Profile Test Plugin. (The cold start profile will be shown on the Test Parameters tab)

 

Figure 4. shows the Measurements and Test Results tab of the Cranking Profile Test plugin in SIVA. This tab displays the input and output profiles for each test pulse. The graphical display on the Test and Measurements tab shows the input and output signals acquired by the oscilloscopes.

Test and Measurements Tab for the PMIC Cranking Profile Test Plugin in SIVA.

Figure 4. Test and Measurements Tab for the PMIC Cranking Profile Test Plugin in SIVA. The graphical display shows the time course of input and output pulses. The input test pulse shown here is that for the warm start test.


 
The PMIC Cranking Profile Test plugin takes advantage of the Hardware Abstraction Layer functionality built in to SIVA framework which makes it easy for a test engineer to use measuring instruments from the suite of PXI instruments.
 
Also available as a separately sold add-on to the PMIC Cranking Profile Test Plugin is DIVE, a waveform tagging, learning and analysis tool that uses Machine Learning Models to simplify the waveform analysis for switching regulator type PMICs. One can train DIVE to classify the waveform scope-shots from the PMIC output terminals as NORMAL or ANOMALOUS or DEFECT1. Some thematic diagrams and screenshots are shown below.

Workflow and Capabilities of DIVE

Figure 5. Workflow and Capabilities of DIVE.

 

PMIC Switching regulator waveform analysis in progress using DIVE.

Figure 6. PMIC Switching regulator waveform analysis in progress using DIVE.

 

*Click below button to Download SIVA Framework Introduction

Other PMIC plugins currently under development: