Solar Telematics System Reliability and Safety Analysis Craig Lechlitner Brian Kelley Clayton Dickemann Dan Ehrman

Block Diagram

PSSCs An ability to track vehicle location using GPS. An ability to receive and send CAN messages from and to other systems in the car. An ability to display graphics on the LCD display. An ability to respond to user input from a touchscreen. An ability to store and load data to and from non-volatile memory.

Components Chosen for Analysis Graphics Controller (PIC24FJ256DA210) Communications Microcontroller (PIC32MX795F512H) SRAM (IS61WV102416BLL) 3.3v Switch Mode Regulator (LM3407)

PIC24 graphics microcontroller High complexity (100 pin, 16 bit) Controls LCD, touch input, audio, SRAM, SD card. Interfaces with PIC32 λp = 3.76 failures per 106 hours MTTF = 266,000 hours = 30.4 years λp = [C1 x πT + C2 x πE] x πQ x πL Parameter Description Value Comments C1 Die complexity 0.28 16 bit microprocessor πT Temperature coefficient 0.60 70 C Die Temperature (estimate) C2 Pin count 0.052 100 pin, Nonhermetic SMT πE Environmental constant 4.0 Ground Mobile πQ Learning factor 1.0 In production for >2 years πL Quality factor 10.0 Commercial Product

PIC32 communications microcontroller High complexity (64 pin, 32 bit) Communicates with other systems on CAN bus, GPS, sends telemetry data. λp = 4.64 failures per 106 hours MTTF = 216,000 hours = 25 years λp = [C1 x πT + C2 x πE] x πQ x πL Parameter Description Value Comments C1 Die complexity 0.56 32 bit microprocessor πT Temperature coefficient 0.60 70 C Die Temperature (estimate) C2 Pin count 0.032 64 pin, Nonhermetic SMT πE Environmental constant 4.0 Ground Mobile πQ Learning factor 1.0 In production for >2 years πL Quality factor 10.0 Commercial Product

SRAM 16 MBit Holds frame buffers for LCD. Interfaces with PIC24. λp = 15.84 failures per 106 hours MTTF = 63,000 hours = 7.2 years λp = [C1 x πT + C2 x πE + λcyc] x πQ x πL MTTF = Parameter Description Value Comments C1 Die complexity 2.48 16MBit,Estimate (table only goes to 1MBit) πT Temperature coefficient 0.60 70 C Die Temperature (estimate) C2 Pin count 0.024 48 pin, Nonhermetic SMT πE Environmental constant 4.0 Ground Mobile λ cyc Cycling induced Failure Rate 0.0 NOT Flotex or Textured-Poly EEPROM πQ Learning factor 1.0 In production for >2 years πL Quality factor 10.0 Commercial Product

LM2673 Switch mode regulator Possible high temperature Powers everything except backlight and audio amplifier 12-15v unregulated input 3.3v, 3Amax regulated output λp = 0.376 failures per 106 hours MTTF = 2,660,000 hours = 304 years λp = [C1 x πT + C2 x πE + λcyc] x πQ x πL MTTF = Parameter Description Value Comments C1 Die complexity .04 Estimate 101 to 1000 MOS transistors (Linear model πT Temperature coefficient 0.60 70 C Die Temperature (estimate) C2 Pin count 0.0034 8 pin, Nonhermetic SMT πE Environmental constant 4.0 Ground Mobile πQ Learning factor 1.0 In production for >2 years πL Quality factor 10.0 Commercial Product

Definition of Criticality levels High - Possibility of injury to user Medium - Renders device useless, major repairs needed Low – Majority of device still works, easily repairable

FMCEA chart Failure mode Possible causes Effect Detection method Criticality Power supply becomes unregulated (Vout > 3.3v) Failure of U5 Possible damage to most ICs, excessive heat build up, smoke and fire Observation (smell of burning electronics), probe 3.3v line High 3.3v Power supply becomes shorted Failure of U5, D5, C19, etc Only backlight works, possible heat build up, smoke and fire Observation (visual, smell of burning electronics), probe 3.3v line Device fails to power up Blown fuse due to temporary short circuit or reverse polarity on VIN Nothing works Observation (visual) Low Pin on either PIC24 or PIC32 becomes constant 1 or 0 Software, poor soldering, failure of peripheral. Specific function stops working Observation Low - Medium Failure to communicate with other systems on CAN bus. Failure of U10 (PIC32), or U13 (MAX 3051), software in this or another system. Cannot control headlights, wiper, vehicle direction. Cannot display battery or solar array stats, etc. Self check Low, can still display vehicle speed/position, vehicle will still drive. Data in SRAM becomes corrupted/unreadable Failure of U3 (SRAM), U1 (PIC24) Erratic data sent to LCD Observation (visual), use logic analyzer

Questions?