13. July 2015 09:00 by Christian in
The automotive OEM EMC requirements analysis is the first step in developing an automotive component level EMC test plan. The technical information made available by product's CTS (Component Technical Specification) is used to:
- review product's family description
- review DUT's theory of operation, physical construction, and vehicle packaging
- identify DUT's functions and measurable I/O test points
- identify critical interface signals
- identify potential sources of emissions
- define performance criteria for each test point during and after each applicable test method listed by OEM EMC specification
1. Product Family Description
- Include a general product family description.
- If the EMC test plan is for more than one product a description of the differences and similarities between the different HW and SW versions must be included.
- If the maximum complexity DUT is used to represent an entire product family include an explanatory justification/rationale. This can be a matrix showing the family and all functions provided by each member of the family where the maximum complexity DUT covers all functions listed.
2. Theory Of Operation
- Include an internal block diagram that clearly show what the DUT does.
- Explain what all DUT's major functions and the internal block diagram.
- Verify the block diagram against the latest vehicle wiring schematics to confirm that shows:
- connections to battery and the ignition switch, including signal inputs such as illumination.
- fuses and their ratings if connected to vehicle battery.
- regulated supply parameters if connected externally to it.
- all external interfaces indicating interactions with other systems, sensors, switches and actuators.
- any special wiring such as twisted and shielded.
- where each signal return or ground wire is connected in the vehicle.
3. Physical Construction
- product package material
- product package location within vehicle
- product package customer access
- number of PCB per package
- number of connectors per package and their drawing indicating their pin out
- product's picture / CAD drawing
- include a module's pin out table and interface description
- description of product's power return ground
- description of product case connection to the reference ground
- show special wiring such as twisted and shielded
- show if the product is connected internally/externally to a magnetically sensitive or controlled device
- show product's connection to vehicle
- specify the type of substrate for each PCB and the number of layers used
4. Identify Critical Interface Signals
- Is there a list of critical signals included in CTS?
- Are the items on the list consistent with information provided in sections 1 & 2?
- Does the I/O table contain all analogue inputs, sensors and communications lines?
- Does the D&R OEM engineer agree with the critical interfaces?
5. Identify Potential Sources of RF Emissions
- Is there a list of potential sources of emissions included in CTS?
- Are they reasonable and consistent with Product complexity?
- Examples of sources of emissions:
- Clocks
- Oscillators
- Communication interfaces
- Local Oscillators
- PWM signals
- Video signals
- There should be no potential sources of emissions around 150-270 KHz or 0.5-2 MHz due to the high risk of interference with radio reception in LW and MW bands.
6. Performance Criteria for each test point during and after each applicable test method
- OEM Spec Test Requirements
- DUT Operating Modes / Functional Classifications
- DUT Input Requirements
- DUT Output Requirements
- Load Box/Test Support Requirements including communication bus
- DUT Activation, Monitoring, and Functional Verification Manual
- DUT Test Set-up Diagram
- Detailed Test Setup and specifics for each OEM Test Method