exact value of adc reference voltage

[bruzzly]

Hi there,

short question. Ist the default reference voltage for the "teensy 3.5" exactly 3.3 V or is it the voltage that can be measured on the "3.3V-Pin", which in my case seams to be 3.3357 V high.

Greetings,
Martin

 

[Theremingenieur]

It's the 3.3V supply voltage which serves as reference. If you need more precision and less noise, you might consider scaling your input signal down and use the internal stabilized 1.2V reference.

 

[bruzzly]

and supply voltage is connected to the "3.3V-Pin", right?

 

[PaulStoffregen]

Yes, more or less.

If you check out the schematic, there's actually some low-pass filtering done with an inductor, resistor and a couple capacitors before the 3.3V power gets to the VREFH pin. But for all practical purposes, you can think of the default reference (not the 1.2V internal one) as connected to the 3.3V power.

https://www.pjrc.com/teensy/schematic.html