Power considerations for automotive use?

Thread Starter

TTBiker

Joined Aug 20, 2018
2
Hi everyone, I recently designed a PCB for automotive use, but have been running into an issue. This circuit uses an Atmel Tiny1616 MCU with a 12bit i2c connected ADC and two i2c connected DACs. It takes an analog input and after a bit of processing it outputs two analog signals through the DACs and a pair of opamp. The problem I'm having is that the circuit works perfect on the bench after many hours of testing, but fails quickly when installed on the vehicle. The MCU gets fried either as soon as a start the vehicle or shortly after. I've been able to determine that the MCU is dying from overvoltage from the regulator. I am using a fixed linear regulator for this circuit, and it is rated to around 26v input. In the latest test the regulator failed to where it outputs a few volts under the input level now, rather than 5v.
My question is if there is special power supply and regulation aspects when used in automotive?
I am working on a redesigning the PCB with a switching regulator, but I need to know if there is just something I am missing.
I am pretty new to PCB design (though I have successfully designed a few previously), so it is pretty likely that I'm missing some design aspect.

Thanks for any suggestions!
 

dl324

Joined Mar 30, 2015
9,140
My question is if there is special power supply and regulation aspects when used in automotive?
Automotive "12V" is very dirty and can have spikes well above 12V. You could try using a TVS diode to protect anything that connects to 12V.

Since TVS diodes tend to fail shorted, you could add a fuse in series. A PTC fuse would be more convenient than a normal fuse.
 

Thread Starter

TTBiker

Joined Aug 20, 2018
2
hi TT,
Welcome to AAC.
I have a Auto Power Electrics PDF that may give you some ideas.

E
EDIT:
Added a PDF Auto transients.
Thank you! I will definitely read through these. Just skimming I've already found some very useful information for my use case.
 
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