CAN Critical Parameters and Setup Considerations for Module Level EMC Testing Jim Lawlis Ford Motor Company Network Communications 1/19/2005

1/19/2005 Jim Lawlis - Ford Motor Company 2 Agenda  CAN Protocol Critical Parameters  CAN Bit Timing  Load Box Termination, CAN Options  Load Box Experiment  Special Considerations for Optical Repeaters  Diagnosing Issues  CAN Emission Reduction

1/19/2005 Jim Lawlis - Ford Motor Company 3 CAN Protocol Critical for Communication Parameters  Arbitration Oscillator ToleranceOscillator Tolerance All delays need to be counted twiceAll delays need to be counted twice  Note: Choke Delays Count 4 Times Rx Tx Rx CAN H CAN L Transceiver ATransceiver B Choke AChoke B

1/19/2005 Jim Lawlis - Ford Motor Company 4 Propagation Delays  Communication Media Number of NodesNumber of Nodes  HS CAN – 16, MSCAN - 32 Capacitance on each NodeCapacitance on each Node  100pF to 130pF Wire LengthWire Length  HS CAN 30 Meters  MS CAN 50 Meters Bus SpeedBus Speed  Twisted Pair 5.5nS/M  Twisted pair With 16 Nodes 6.6nS/M  Twisted Pair with 32 Nodes 8.0nS/M

1/19/2005 Jim Lawlis - Ford Motor Company 5 CAN Load Box Configuration  CAN Bit Timing Settings  Monitor Mode  Load Box Termination  Data Monitoring – Need to Check the Data, Not Just that Can Traffic is Present  Monitor Error Frames/Bus off

1/19/2005 Jim Lawlis - Ford Motor Company 6 CAN Bit Timing Basics  The CAN bit  Measuring Total Delays  J2284 equations  The Bit Timing Spreadsheet

1/19/2005 Jim Lawlis - Ford Motor Company 7 The CAN Bit

1/19/2005 Jim Lawlis - Ford Motor Company 8 Measuring Total Delays  Measure from the TX of one to the RX of an identical Module. Rx Tx Rx CAN H CAN L Transceiver ATransceiver B Choke AChoke B

1/19/2005 Jim Lawlis - Ford Motor Company 9 J2284 Equations  Created by Karl Overberg of Ford and Dr. Dietmayer of Philips  Bench Validated with Ford internally Designed Modules  Vehicle Validated on a Fleet Consisting of Police Vehicles, High End Ford Vehicles, Heavy Truck

1/19/2005 Jim Lawlis - Ford Motor Company 10 The Bit Timing Spreadsheet

1/19/2005 Jim Lawlis - Ford Motor Company 11 CAN Monitor Only Load Boxes  Note: CAN is an all Node ACK or NACK Protocol  You may think you are only Monitoring. Unless the tool has a Monitor Only Option and it has been Enabled, the load box is Participating in Communication!!!

1/19/2005 Jim Lawlis - Ford Motor Company 12 Termination Methods  Termination Methods Terminated NodesTerminated Nodes  Standard Termination  Split Termination Test Tool TerminationTest Tool Termination  A/C Termination (ISO 15765, Part 4, section )

1/19/2005 Jim Lawlis - Ford Motor Company 13 Load Box Termination Terminated NodesNon-Terminated Nodes ~ 60 Ohm 1% 4.7nF

1/19/2005 Jim Lawlis - Ford Motor Company 14 Chamber Set-Up  Tool is Configured  Delays Have been identified/Checked  How do We Connect the Load Box to the set up in the chamber?

1/19/2005 Jim Lawlis - Ford Motor Company 15 CAN Load Box Experiment  Parameters That Need to be Defined Board to Case (A/C, D/C, Open)Board to Case (A/C, D/C, Open) Case to ground plane (On Ground Plane, 5 cm Above ground plane)Case to ground plane (On Ground Plane, 5 cm Above ground plane) Network Load box to system Load box power wiring (On Ground Plane, 5 cm Above Ground Plane)Network Load box to system Load box power wiring (On Ground Plane, 5 cm Above Ground Plane)  A full Factorial Experiment was run because it provides the most information and 12 runs were possible

1/19/2005 Jim Lawlis - Ford Motor Company 16 Experiment Setup Y Performance = X1 X2 X3 X1 = Routing (5cm or Ground Plane) X2 = Case to Table (5cm or Ground Plane) X3 = Board to Case (AC, DC, or Open) DUT Load Box Metal Case X2X2 Ground Plane CAN Tool X3X3 Power Ground CAN_H CAN_L Make these lines as short as possible X1X1

1/19/2005 Jim Lawlis - Ford Motor Company 17 Experiment Analysis  Previous Experience determined the worst case Load Box Setup noise was observed in the Vertical BICON 30 to 200Mhz  Area of violations above the limit line were measured and calculated for each test  The Best Performance was Identified

1/19/2005 Jim Lawlis - Ford Motor Company 18 DOE Test Matrix Run OrderPower RoutingCase to TableBoard to Case 1GND A/C 25cmGNDA/C 3GND5cmA/C 45cm A/C 5GND D/C 65cmGNDD/C 7GND5cmD/C 85cm D/C 9GND Open 105cmGNDOpen 11GND5cmOpen 125cm Open

1/19/2005 Jim Lawlis - Ford Motor Company 19 Experiment Data

1/19/2005 Jim Lawlis - Ford Motor Company 20 Data Processing  Normality of the Data and Residuals  Minitab DOE Analysis  Multi-Variable Chart  Interaction Plot  Main Effects Plot

1/19/2005 Jim Lawlis - Ford Motor Company 21 Normality of Data

1/19/2005 Jim Lawlis - Ford Motor Company 22 Normality of Residuals

1/19/2005 Jim Lawlis - Ford Motor Company 23 Minitab DOE Analysis General Linear Model: Data 2 versus Power Routin, Case to Tabl,... Factor Type Levels Values Power Ro fixed 2 GND 5cm Case to fixed 2 GND 5cm Board to fixed 3 AC DC Open Analysis of Variance for Data 2, using Adjusted SS for Tests Source DF Seq SS Adj SS Adj MS F P Power Ro Case to Board to Power Ro*Case to Power Ro*Board to Case to*Board to Error Total

1/19/2005 Jim Lawlis - Ford Motor Company 24 Multi-Variable Chart

1/19/2005 Jim Lawlis - Ford Motor Company 25 Interactions Plot

1/19/2005 Jim Lawlis - Ford Motor Company 26 Main Effects Plot

1/19/2005 Jim Lawlis - Ford Motor Company 27 Experiment Results DUT Load Box Metal Case GND Ground Plane See EMC ES-XW7T-1A278-A(X) (X): Recent Version CAN Tool Board to Case DC GND Power Ground CAN_H CAN_L Make these lines as short as possible

1/19/2005 Jim Lawlis - Ford Motor Company 28 Monitoring CAN through Optical Repeaters  The Signal Delay of a Typical Optical Repeater (wire to optical to wire) will be ~300ns  This does not include the signal delay through the Optical Cable ~5.0ns/meter.

1/19/2005 Jim Lawlis - Ford Motor Company 29 Network Length Penalty for Optical Repeaters  Assume Tool uses a Crystal  Fast Tool Transceiver (Combined RX and TX delays less than 255ns vs. 330ns)  Communication and Arbitration can be Guaranteed through 24 meters Tool to Furthest Module

1/19/2005 Jim Lawlis - Ford Motor Company 30 Diagnosing Issues  No Substitute for an Oscilloscope  Just turning off CAN communication will not tell the story. You need to rerun with the TX pin shorted to the dominant state. This shows the noise on the 5 Volt feed as well as on the ground of the node.  CAN tools need to make assumptions  Advantages of monitoring the Common Mode and Differential Mode signals

1/19/2005 Jim Lawlis - Ford Motor Company 31 CAN Radiated Emission Reduction Methods  Overall Goal  Communication Bus Noise will always be Low Frequency. High Frequency Noise is due to Setup issues  Ferrites  Chokes  Split Termination

1/19/2005 Jim Lawlis - Ford Motor Company 32 Base Line Rod

1/19/2005 Jim Lawlis - Ford Motor Company 33 Baseline BICON

1/19/2005 Jim Lawlis - Ford Motor Company 34 Ferrites Rod

1/19/2005 Jim Lawlis - Ford Motor Company 35 Ferrites BICON

1/19/2005 Jim Lawlis - Ford Motor Company 36 Choke 51uH Rod

1/19/2005 Jim Lawlis - Ford Motor Company 37 Choke 51uH BICON

1/19/2005 Jim Lawlis - Ford Motor Company 38 Split Termination Rod

1/19/2005 Jim Lawlis - Ford Motor Company 39 Split Termination BICON

1/19/2005 Jim Lawlis - Ford Motor Company 40 Next Issues  Wake/Sleep Bus Recessive State Loading Not a lot of information availableNot a lot of information available  Questions/Discussion