Signal coupled in power supply (3.3V) of STM32F103 during spark:
Is there any benefit to using this diode (circled in red) or not (without this diode the snubber circuit will start working)?
What is a better solution/topology to avoid noise and maintain the spark efficiency?
My doubt is:
If I use this shown configuration, is it more difficult to cut-off the SCR (maintain hold current for a long period) and can it disturb another part in circuit?
I use an automotive sparkplug resistive cable with 4K ohms and a earth strap to connect the engine with ignition coil GND (frame).
The diode D4 is relevant during the C3 charging, is it a necessary solution or does it not make a big difference in this circuit?