1. ECE477 Team 6: The Soviet Challenge
FMECA worksheet presentation

2. Criticality measures Low High
General annoyance – screen stops working, buttons don’t work
λ < 10-6
High
Parts get dangerously hot,
catch fire, and/or explode
λ < 10-9

3. Schematic

4. Battery Pack – “A”

5. Battery Pack – “A” Failure No. Failure Mode Possible Causes
Failure Effects
Method of Detection
Criticality
Remarks A1
Header Output 1 = 0V
Battery Disconnected, Battery dead, Protection circuit failure
Device is inoperable
Observation
Low A2
Header Output 2 = 0V
U19 (DS2781) failure, R74 damaged, Battery dead
Unable to track battery life via uC, in the cases of U19, R74 failure A3
Battery Shorted out
Traces in battery circuit short out, wiring from battery terminals short out
Battery discharges VERY rapidly (Protection circuit keeps from exploding)
High A4
Header output 1 > 8.4V
Protection circuit failure
Battery becomes overcharged, can lead to overheating, possibly explosion

6. 3.3V Regulator – “B”

7. 3.3V Regulator – “B” Failure No. Failure Mode Possible Causes
Failure Effects
Method of Detection
Criticality
Remarks B1
PWR_3.3 < 3.3V
U20
(LTC ) failure
Circuit becomes underpowered, device is inoperable
Observation
Low B2
PWR_3.3 > 3.3V
U20 damaged
Other components in circuit could be damaged by overvoltage
High B3
PWR_ON+ > 14.4V
Short in SW4 between PWR_ON+ and PWR_OFF+, along with a failure of U18 (MAX846A)
Damage to U20, can lead to B2 happening

8. Battery Recharger – “C”

9. Battery Recharger – “C”
Failure No.
Failure Mode
Possible Causes
Failure Effects
Method of Detection
Criticality
Remarks C1
PWR_OFF+ <8.4V
Wall Wart disconnected, R76, R75 or, R70 short
Battery won’t charge completely
Observation
Low C2
PWR_OFF+ >8.4V
U18 (MAX846A) Damaged, short in recharger, R76, R75, or R70 damaged
Battery runs the risk of being overcharged if protection circuit has failed
High C3
Conn Jack Pwr input >21V
Power surge from outlet
U18 damaged

10. Compact Flash Circuit – “D”

11. Compact Flash Circuit – “D”
Failure No.
Failure Mode
Possible Causes
Failure Effects
Method of Detection
Criticality
Remarks D1
No transmission from CompactFlash card
CF card disconnected or loose, PWR disconnected, software
TetriNET will not be playable online.
Observation
Low

12. Microcontroller Circuit – “E”

13. Microcontroller Circuit – “E”
Failure No.
Failure Mode
Possible Causes
Failure Effects
Method of Detection
Criticality
Remarks E1
Continual resetting
Y1, C26, C27 – problem with the crystal circuit,
software
Device will be inoperable
Observation
Low E2
Timer overflow
A game of TetriNET lasts longer than days
Code will have erratic effects

14. Button Circuit – “F”

15. Button Circuit – “F” Failure No. Failure Mode Possible Causes
Failure Effects
Method of Detection
Criticality
Remarks F1
Buttons don’t register inputs
BTN_SEL not changing, U17 (ATF16LV8C) damaged, button wiring loose
Device cannot be properly operated
Observation
Low

16. LCD Circuit – “G”

17. LCD Circuit – “G” Failure No. Failure Mode Possible Causes
Failure Effects
Method of Detection
Criticality
Remarks G1
Displays nothing
U4/U5 (LCD headers) connectors damaged or loose, ezLCD-001 damaged
Device cannot be used
Observation
Low G2
Displays gibberish
Software error, ezLCD-001 damaged, header connections not secure
Device unstable or unusable

18. Reprogramming Circuit – “H”

19. Reprogramming Circuit – “H”
Failure No.
Failure Mode
Possible Causes
Failure Effects
Method of Detection
Criticality
Remarks H1
Circuit cannot be reprogrammed
U9/U10 (ISP/JTAG headers) damaged or loose
Cannot reprogram microcontroller
Observation
Low