Hello,

I'm developing a analog input (using module ADC of my uController) and i've getting problem with thermal stability when the temperature rise. Nawadays I'm using a schottky diode to +VCC (that its 2,5V - voltage reference of my ADC) to clamp between 2,7V ... 2,8V when the user put a higher voltage (that the circuit doesnt support).

In my mind, there are two possibilities: using schottky (to 2,5V) or zener diode (to GND), however both might not looks stable when temperature rise because reverse/leakage current increase. Anyone could help me with this problem?

Thank you.

B.R.

 

Check out this .........
It's Temperature-Compensated, and Adjustable.
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Hi Low, thank you by reply.

My reference is with TL431 (of my analog input, and my microcontroller).

Follow my circuit typical:

When i put off the diode D1, the circuit maintain stable with temperature rise (20 and 70oC). When i put on circuit, the circuit deviate.

 

D1 should go to Vdd, not Vref.

 

Hello.

The maximum signal at analog inputs in this microcontroller it's AVdd + 0,3 (and my Avdd its Vref, so the diode should go to Vref to clamp when signal rise after 2,8V).

 

my Avdd its Vref

Why?
Normally Avdd and Vref are two different voltages since AVdd typically has a lot of digital noise..

Don't you have 3.3V or 5V to operate the micro?
So the micro works ok on only 2.5V?