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

2. Block Diagram

3. 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.

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

5. 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

6. 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

7. SRAM 16 MBit Holds frame buffers for LCD. Interfaces with PIC24.
λp = 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

8. LM2673 Switch mode regulator
Possible high temperature
Powers everything except backlight and audio amplifier
12-15v unregulated input
3.3v, 3Amax regulated output
λp = 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

9. 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

10. 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

11. Questions?