Teensy 4.0 fried - posting project schematic to make sure I didn't do anything wrong

[inevitable jambalaya]

Hi,

My teensy has gone to the great recycler. I think I might have accidently touched one of the u controller pins with a 9V source, but I wanted to make sure that there is nothing in the circuit design that might have caused this. I am posting the schematic in the hopes that someone will give it a quick look over and let me know if something looks wrong.

Note that the circuit worked as intended the first time, but not the second time, and between the two I did disconnect and then reconnect the 9V source.

Thanks for your help!

[fdaniels]

Not that i am a pro in electronics, but shoudnt the batteries GND be somehow connected to the Teensys GND?

[inevitable jambalaya]

You are correct!

However, the error was on the schematic only. The circuit itself did contain a common ground for the 3v AND 9v power supplies.

I've included a new schematic to fix the mistake.

Good catch

[sbfreddie]

Jambalaya:
I am guessing you did not read the data sheet for the DRV 8837. The schematic your posted shows this to be true.
Please reread the data sheet, specifically page 19 which I will attach below.
In perusing the data sheet I do not see any way the DRV8837 could back-feed any kind of destructive voltage spikes to the Teensy, so the only conclusion I could draw from the limited information you have provided is what you have admitted to in the first post.
Regards,
Ed