Teensy powered by symmetrical supply

C

ClemensW

New member
To avoid level shifting opamps I decided to power the teensy with a symmetrical power supply.
The teensy digital ground is at -1.66V and Teesy Vin pin is at 2.5V. Thus, the total voltage across Vin and GND is 4.16V. To correct DC offset errors, the analog ground (0V) is read at an analog pin of the teensy and subtracted from any signal that is read at any other analog input pins. The result is perfectly symmetrical waveforms around 0.

While that system is performing normally well, two teensies burned presumably because of a loose contact on the analog ground or positive supply.
I was wondering if I should add a resistor between the analog ground and the teensy analog input pin to reduce currents. But I'm not sure if the issue could stem from that ground connected to the input pin at all.

Any comments an this are welcome!
 
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A 1K resistor in series with the ADC input might help. Maybe. I'm honestly having a hard time envisioning how this power supply is built.

Also don't know what Teensy model you're using. Guessing Teensy 4.0 or 4.1?

Something thing to consider is the startup and shutdown performance, whether any pins are possibly driven above 3.3V or below GND (from Teensy's point of view). You might also look at whether the power supplies have any overshoot behavior during startup. Startup overshoot is sometimes a big problem with small DC-DC converter modules, especially if they don't have enough extra capacitance added at their input or too much added at their output.
 
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