fram wrote: ↑
Sat Feb 27, 2021 9:36 am
As you said, you should be ok with SOT223 package for LDO, according to voltage drop , thermal copper mass and thermal resistance of the casing. (i measured a static current of 70mA for speeduino in this kind of small design, so not big deal for the LDO)
Ona last thing you can do is to shield the crystal with ground vias all over the cristal.
This design should work, the only thing i don't know will be the behaviour of the IGBT. (think about adding a top heatsink)
BTW, you will not use any sensor interface IC for Cranck/Cam signals?
I added some ground vias around the crystal. The crystal housing itself is grounded to two of the four pads. You are correct in estimating around 70mA, with a very similar design I was consuming 0.5 - 0.6 mA according to my supply.
My only real concerns with the IGBT are that I am not placing any gate resistor or gate pulldown on the board. However, the IGBT has both already inside, a 110 ohm gate resistor and a 10k-30kohm pull down. Should be good, according to the datasheet, but it is a point of concern for me. A bigger concern is general noise from the IGBT causing the controller to lock up. I would like to do my best to avoid this at all cost. However, the way the circuit is designed, I can pull the IGBT off the board and run the gate drivers logic output directly to the main connector.
The crank and cam signals are intended to be logic level (open drain NPN). On my project I am only using a Hall sensor for a crank signal. I know this limits the type of sensors that can be used for motion detection, but I have accepted that.
Thanks again for all the help and suggestions, I will be sure to continue implementing your recommendations in future designs.
"Arguing with an Engineer is a lot like wrestling in the mud with a pig. After a couple of hours you realize the pig likes it."