Reliability and Safety AnalysisTeam 12: Android Street Car

Zongyang Zhu

Components Chosen

NXP LPC1768 ARM-M3 32bit microcontroller TI TPS62160 Step-down Converter L298 Dual H-Bridge

Microcontroller

LPC 1768 32bit ARM-M3 uCMIL-Hdbk-217F model: Microprocessorsλp = (C1*πT+C2*πE)*πQ*πLC1 Die complexity failure fate 0.56 32 bit uC

πT Temperature coefficient 3.1 Tj <= 125C

C2 Package failure rate 0.068 128 pin SMT

πE Environment factor 4 Ground mobile

πQ Quality factor 10 commercial product

πL Learning factor 1 more than 2 years

λp # failures/10^6 hr 20.08 (C1*πT+C2*πE)*πQ*πL

MTTF mean time to fail (in years) 5.68 1/λp

Power Supply

TPS62160 Switching RegulatorMIL-Hdbk-217F model: MOS and Digital Devicesλp = (C1*πT+C2*πE)*πQ*πLC1 Die complexity failure fate 0.04 <= 1000 transistors

πT Temperature coefficient 3.1 Tj <= 125C

C2 Package failure rate 0.0034 8 pin SMT

πE Environment factor 4 Ground mobile

πQ Quality factor 10 commercial product

πL Learning factor 1 more than 2 years

λp # failures/10^6 hr 1.376 (C1*πT+C2*πE)*πQ*πL

MTTF mean time to fail (in years) 82.85 1/λp

Motor Control

L298 Dual H-BridgeMIL-Hdbk-217F model: Microprocessorsλp = (C1*πT+C2*πE)*πQ*πLC1 Die complexity failure fate 0.01 <= 100 transistors

πT Temperature coefficient 58 Tj <= 150C

C2 Package failure rate 0.0056 15 pin SMT

πE Environment factor 4 Ground mobile

πQ Quality factor 10 commercial product

πL Learning factor 1 more than 2 years

λp # failures/10^6 hr 6.024 (C1*πT+C2*πE)*πQ*πL

MTTF mean time to fail (in years) 18.92 1/λp

Criticality Levels

High Criticality Possibility to cause injuries Acceptable mean failure rate 10-9

Medium Criticality Overheating of components

Acceptable mean failure rate 10-7

Lower Criticality Failure is easily recoverable

Acceptable mean failure rate 10-6

Schematic – Power Supply

Schematic - Microcontroller

FMECA - Microcontroller

Failure No. Failure mode Possible Cause Failure Effects Method of

Detection Criticality

A1 no clock in uC damaged 12 crystal no output from uC, cannot enter ISP mode Observation Low

A2currupt data output at SPI/UART

cold joint at headers system not responsive Observation Low

A3 VCC = 0V Bypass capacitor breakdown

Overheating of power supply Observation Medium

FMECA - Others

Failure No. Failure mode Possible Cause Failure Effects Method of

Detection Criticality

B1 power supply Vout=0 R1 is open no power for the whole

system Observation Low

B2 power supply overheating

C2, C3, C4 breakdown

overheating, no power for system Observation Medium

C1 hbridge no output Hbridge failure system can respond but

no motion Observation Low

Questions?