Josh Piron, Jacob Pfister, Kevin Templar, Mike Phillips Group Nine Reliability and Safety Analysis DART

Components Chosen for Analysis dsPIC33FJ128MC804 Microcontroller Samples the sensors, updates LCD, writes data to SD card Standalone Linear Li-Ion Battery Charger (ltc ) Responsible for charging the battery Synchronous Boost Converter (TPS61031PWP) Boosts wall wart or battery to 5V

Reliability and Safety Criticality Levels – Low Loss of non-core functionality of the device – Medium Loss of core functionality of the device (microcontroller, LCD, SD card system) – High Possible injury to the user or noticeable physical damage of the device

FEMCA - Microcontroller Failure No. Failure ModePossible Causes Failure Effects Method of Detection CriticalityRemarks 1AMicrocontroller stays in reset mode Reset circuit or switch is broken Device produces no meaningful output Observable – nothing lights up, nothing on LCD display MediumSystem loses core functionality (non- operational) 1BMicrocontroller outputs no data to peripherals No power to the microcontrolle r or voltage out of tolerance (3V to 3.3V) Device produces no meaningful output Observable – nothing lights up, nothing on LCD display MediumSystem loses core functionality (non- operational) 1CPin sticks at 0 or 1 Pin driver burned out by over voltage on pin Peripherals display/recor d meaningless data or microcontroll er reads meaningless data Observable – LCD display or SD data is not meaningful Low/ Medium System loses some functionality which may result in a loss of core functionality of the device

Failure No. Failure ModePossible Causes Failure Effects Method of Detection CriticalityRemarks 2ABattery charger outputs 0V Battery charger IC fried Battery does not charge Battery stays uncharged MediumSystem no longer portable 2BBattery charger overvolts the battery Battery charger IC fried Battery could catch fire or explode ObservableHighPotential catastrophic destruction and potential harm to the user 2CBattery charger overcharges the battery Battery charge detection pin is fried Battery could catch fire or explode ObservableHighPotential catastrophic destruction and potential harm to the user FEMCA – Battery Charger

FEMCA – Boost Regulator Failure No. Failure ModePossible Causes Failure Effects Method of Detection CriticalityRemarks 3ABoost outputs 0V Boost IC friedDevice produces no meaningful output Observable – nothing lights up, nothing on LCD display MediumSystem loses core functionality (non- operational) 3BBoost outputs >>3.3V Boost IC fried or input voltage >> 3.3V All 3.3V peripherals fry or cease to be usable by the microcontroller Observable – no meaningful output, device may get hot Medium/ High System loses core functionality (non- operational micro/peripherials) and system could overheat

MTTF dsPIC33FJ128MC804 Microcontroller years Standalone Linear Li-Ion Battery Charger (ltc ) years Synchronous Boost Converter (TPS61031PWP) 6.48 years

Questions?