- Wed Sep 16, 2020 2:33 pm
#45396
noisymime wrote: ↑Wed Sep 16, 2020 7:19 amAn ideal diode can be used for reverse voltage protection, the spec was written years ago and is basically 4.75V minimum processor voltage + a diode drop + the LDO losses, the 5V doesn't need to be stable it can be allowed to drop as long as it doesn't go below the minimum voltage required for safe operation of the processor, the sensors are ratiometric. I doubt if there are any ECUs that use LDOs for the front end regulator these days and 5V is still the norm for engine management syestems to maintain ruggedness and noise immunity. Buck/boost systems are certainly used in some ECUs, the standard is a minimum requirement and manufacturers often specify more stringent conditions - VW80808 specifies 2.5V for the cranking waveform for diesel engines.JHolland wrote: ↑Mon Sep 14, 2020 9:13 am The automotive standard (ISO16750) calls for operation down to 6V during cranking.That's an interesting requirement. It realistically means you either must be using a switching regulator or need to run a 3v3 system (Though given most automotive sensors are 5v, that would still be challenging). I can't see any way of meeting that requirement using an LDO and reverse polarity protection unless you throw in something like a buck/boost, which brings it's own resiliency problems