ADC dynamic range : How can I the maximum ADC conversion precision ?

[Simon NOWAK]

Posted on March 09, 2017 at 09:27

Hi everyone,

I work with the stm32l073rz. I  measure the sensor with the ADC and the retrieved value is correct.

Now, I want to increase the precision. The sensor gives a little value (maximum 1.5V). Can I reduce the intern ADC voltage to increase the precision like this figure ?

Thank you very much for your help

Regards

Simon

#nucleo: #adc #vref+ #stm32l0

[S.Ma]

Posted on March 09, 2017 at 09:52

Assuming calibration is done, using oversampling (if possible) would be the first step to less noise.

The VDDA should be a clean non noisy source (PSSR power rejection impacting the precision and performance).

In theory, reducing VDDA might help 'less than' a bit. Your main goal is to reduce the SNR.

If the signal is not random and is characterized, digital filtering post processing may also help.

[Simon NOWAK]

Posted on March 10, 2017 at 10:26

Hi,

Thanks for your answer, you helped me.

Now, I write in the CFGR2 register to modify the oversampling ratio but I have a problem to re-activate the CKMODE bits. 

I can't never write in

the CKMODE bits, I can just reset this bits. 

Regard,

Simon

[AvaTar]

Posted on March 10, 2017 at 10:42

Wouldn't adding a buffer amplifier (x 2.2 = 3.3V / 1.5V) do the same job ?

It would relax possible input impedance issues as well.