ADC producing noise

Alex PEPY

Hi,

I'm facing to an issue on my F28069 Experimenter's kit :

It is about one ADC (ADCINA0) which generates some noise on the signal it has to convert. And this noise is REALLY huge (about 250mV) !

This pic shows the input signal for the ADC when it's not connected to the ADC.

This one shows the noise induced by the ADC when connected to the signal.

Regards,

Alex

over 12 years ago

0 Igor Gorbachev over 12 years ago

Guru 20525 points

Hello!

I think at first it will be useful for you http://e2e.ti.com/support/microcontrollers/c2000/f/171/t/264395.aspx.

Regards,

Igor

0 Gautam Iyer over 12 years ago

Guru 192875 points

Hi Alex,

Go through this post for more info on ADC accuracy.

http://e2e.ti.com/support/microcontrollers/c2000/f/171/t/264395.aspx

Regards,

Gautam

0 Igor Gorbachev over 12 years ago in reply to Gautam Iyer

Guru 20525 points

Hello Gautam!

I think that's your problem at 100%!

Regards,

Igor

0 Alex PEPY over 12 years ago in reply to Gautam Iyer

Prodigy 180 points

Thanks for your response, I saw this post when I search on E2E but unfortunately the noise is always here whatever I'm using internal references for ADC or VREFHI/VREFLO pins.

The ground is common for all my components, the input is fine when it's not connected to the ADCINA0 but I get this noise only when it's connected.

The F28069 is powered by the USB, I don't see any noise on the power signal.

Maybe I'll seperate Analog and Digital ground like Gautam did and see what happens.

0 Gautam Iyer over 12 years ago in reply to Alex PEPY

Guru 192875 points

Hi Alex,

Also can you check the results by testing the sample code for F28069. Because 250mV noise is way too much and there might be some issue with adc initialization. Else some hardware issue. Check thoroughly and revert.

Regards,

Gautam

0 Igor Gorbachev over 12 years ago in reply to Alex PEPY

Guru 20525 points

Hello Alex!

By the way. "Maybe I'll seperate Analog and Digital ground" - It makes sense to try too.

Regards,

Igor

0 Alex PEPY over 12 years ago in reply to Gautam Iyer

Prodigy 180 points

I tested the example before using the ADC for my project. And it was working fine.

I guess my issue is about hardware. But what I don't understand is how the ADC (which is an input w/o any consumption) can generate a huge noise on my signal.

As soon I connect my signal to ADC, the noise appears...

0 Igor Gorbachev over 12 years ago in reply to Alex PEPY

Guru 20525 points

Hello!

ADC does not generate such big noise. ADC only measures that one has at its input. At your case It seems that the induced interference takes place in the chain connecting the measured signal.

Regards,

Igor

0 Gautam Iyer over 12 years ago in reply to Alex PEPY

Guru 192875 points

I totally agree with Igor, please check your hardware and also observe signals on a DSO for detecting any interfering signals (if any).

Regards,

Gautam

0 Alex PEPY over 12 years ago in reply to Gautam Iyer

Prodigy 180 points

Well, well, well, I just disconnected the ADC from the signal (when the system wasn't powered of course) and when I powered it up, the ground wire melts (in a plume of smoke).

That's a thing I've done many times before without problems, so I guess I have now some HUGE hardware problems.

So my ADC issue is in standby for now...

Regards,

Alex

0 Gautam Iyer over 12 years ago in reply to Alex PEPY

Guru 192875 points

Hi Alex,

Good good, atleast the problem has been spotted. The most important thing that you've to do is check the isolation between Vdd and ground pins for both dock and card. Also check whether the IC's getting heated up or not.

Regards,

Gautam Iyer

C2000™︎ microcontrollers

C2000 microcontrollers forum

ADC producing noise