CAN Critical Parameters and Setup Considerations for Module

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

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

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

Propagation Delays u Communication Media • Number of Nodes u HS CAN – 16, MSCAN - 32 • Capacitance on each Node u 100 p. F to 130 p. F • Wire Length HS CAN 30 Meters u MS CAN 50 Meters u • Bus Speed Twisted Pair 5. 5 n. S/M u Twisted pair With 16 Nodes 6. 6 n. S/M u Twisted Pair with 32 Nodes 8. 0 n. S/M u 1/19/2005 Jim Lawlis - Ford Motor Company 4

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

CAN Bit Timing Basics The CAN bit u Measuring Total Delays u J 2284 equations u The Bit Timing Spreadsheet u 1/19/2005 Jim Lawlis - Ford Motor Company 6

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

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

J 2284 Equations Created by Karl Overberg of Ford and Dr. Dietmayer of Philips u Bench Validated with Ford internally Designed Modules u Vehicle Validated on a Fleet Consisting of Police Vehicles, High End Ford Vehicles, Heavy Truck u 1/19/2005 Jim Lawlis - Ford Motor Company 9

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

CAN Monitor Only Load Boxes Note: CAN is an all Node ACK or NACK Protocol u 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!!! u 1/19/2005 Jim Lawlis - Ford Motor Company 11

Termination Methods u Termination Methods • Terminated Nodes Standard Termination u Split Termination u • Test Tool Termination u 1/19/2005 A/C Termination (ISO 15765, Part 4, section 9. 4. 1. 3) Jim Lawlis - Ford Motor Company 12

Load Box Termination Terminated Nodes Non-Terminated Nodes ~ 60 Ohm 1% 4. 7 n. F ~ 60 Ohm 1% 1/19/2005 Jim Lawlis - Ford Motor Company ~ 60 Ohm 1% 4. 7 n. F ~ 60 Ohm 1% 13

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

CAN Load Box Experiment u Parameters That Need to be Defined • Board to Case (A/C, D/C, Open) • 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) u 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 15

Experiment Setup Y Performance = X 1 X 2 X 3 X 1 = Routing (5 cm or Ground Plane) X 2 = Case to Table (5 cm or Ground Plane) X 3 = Board to Case (AC, DC, or Open) Metal Case X 1 Power Ground DUT Load Box CAN_H CAN_L Make these lines as short as possible 1/19/2005 Jim Lawlis - Ford Motor Company CAN Tool X 3 X 2 Ground Plane 16

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

DOE Test Matrix Run O r d e r Power Routi ng Case to Tabl e Board to Case 1 GND A/C 2 5 cm GND A/C 3 GND 5 cm A/C 4 5 cm A/C 5 GND D/C 6 5 cm GND D/C 7 GND 5 cm D/C 8 5 cm D/C 9 GND Open 10 5 cm GND Open 11 GND 5 cm Open 12 5 cm Open 1/19/2005 Jim Lawlis - Ford Motor Company 18

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

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

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

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

Minitab DOE Analysis General Linear Model: Data 2 versus Power Routin, Case to Tabl, . . . Factor Type Levels Values Power Ro fixed 2 GND 5 cm Case to fixed 2 GND 5 cm Board to fixed 3 AC DC Open Analysis of Variance for Data 2, using Adjusted SS for Tests Source DF Seq SS Adj MS F Power Ro 1 675. 00 8. 70 Case to 1 280. 33 3. 61 Board to 2 296. 17 148. 08 1. 91 Power Ro*Case to 1 320. 33 4. 13 Power Ro*Board to 2 420. 50 210. 25 2. 71 Case to*Board to 2 2276. 17 1138. 08 14. 67 Error 2 155. 17 77. 58 Total 11 4423. 67 1/19/2005 Jim Lawlis - Ford Motor Company P 0. 098 0. 198 0. 344 0. 179 0. 270 0. 064 23

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

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

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

Experiment Results Metal Case DUT Load Box Power Ground CAN_H CAN_L Make these lines as short as possible CAN Tool Board to Case DC GND Ground Plane See EMC ES-XW 7 T-1 A 278 -A(X) (X): Recent Version 1/19/2005 Jim Lawlis - Ford Motor Company 27

Monitoring CAN through Optical Repeaters The Signal Delay of a Typical Optical Repeater (wire to optical to wire) will be ~300 ns u This does not include the signal delay through the Optical Cable ~5. 0 ns/meter. u 1/19/2005 Jim Lawlis - Ford Motor Company 28

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

Diagnosing Issues u u 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 30

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

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

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

Choke 51 u. H Rod 1/19/2005 Jim Lawlis - Ford Motor Company 36

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