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What is the effect of 100 microseconds(us) transient in a automobile battery?

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A typical embedded system, let's say Transmission or Power Train Electronic Control Unit (ECU) is powered by automobile Battery.

Battery voltage is at 12 Volts. If the battery voltage drops to 0 Volts in 5 us and stays at 0 V for 100 us, then rises back to 12V in 5 us, what impact will this have on Microcontroller memories, different microcontrollers inputs like Analog, Digital, PWM, etc. And different outputs like Digital, PWM etc.

Will the contents of I/O and memories like SRAM, Program Flash, Data Flash change due to this transient?

The microcontroller on the ECU is Infineon Aurix TX29x.


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Without some knowledge concerning power "backup" for the ECU, i.e., capacitive reserve, etc., there's no way to predict uC response to your scenario.


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There will be a regulator between the 12V input and the microcontroller, which is likely running on 3.3V or 5V. Also likely, there will be an input capacitor on the 12V side of the regulator, and another on the output side of the regulator. Tell us how big those capacitors are, and how much current flows through the regulator, and we can answer your query.

My guess is that there is enough Q stored to run the ECU for 100uS and quite a bit longer...
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FWIW 12V automotive systems run at about 14 to 15V. Devices used with automotive power systems need to handle somewhat ugly power. They sell regulators designed for use in autos. These handle the spikes. As for power dropout I agree with bob and mike.
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