Possible Causes for ADC Input to be high

hhuynh

Hello,

I just recently started to program my F28034PN chip. I've been trying out the ADC functionality. I followed the example project, Example_2803xAdcSoc. It seems that input is always reading 4095 even with no input applied. I tried downloading the example project to my chip. I still get the same results. What could be the possible causes for the reading to be high?

over 10 years ago

0 Frank Ankapong over 10 years ago

TI__Mastermind 28275 points

Hi hhuynh,

If the input is floating, try tying it to some fixed voltage. You can try ground.

0 Joe Prushing over 10 years ago in reply to Frank Ankapong

TI__Genius 16521 points

Hi hhuynh,

Is this custom or TI hardware? If custom, please make sure VREFLO (pin 22) is properly grounded to VSSA.

Regards,

Joe

0 hhuynh over 10 years ago in reply to Joe Prushing

Prodigy 20 points

Joe,

My apologies for the late reply. It is custom. I will try your and Franks suggestion.

Thanks,

Hung

0 GURU B over 10 years ago in reply to Joe Prushing

Prodigy 60 points

Hi Joe/Frank,

I am working with Hung on this project..
Pin 22 is properly grounded to VSSA
We tried providing a fixed voltage from 0V to 1V on the inputs, it still read 4095. What could be the possible issue here ?

On our system we are only using a couple of ADC inputs and the remaining ADC inputs are floating.
Does the floating ADC ports effect the performance of the ADC pins being used ?

Regards,
Guru

0 Frank Ankapong over 10 years ago in reply to GURU B

TI__Mastermind 28275 points

Hi Guru,

Is your Vrefhi tied to 3.3v?

0 GURU B over 10 years ago in reply to Frank Ankapong

Prodigy 60 points

Yes

0 Frank Ankapong over 10 years ago in reply to GURU B

TI__Mastermind 28275 points

Hi Guru,

I apologize if this seems like a rudimentary question, just trying to rule out any setup issue. What about Vdda, is it also tied to 3.3v?

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Possible Causes for ADC Input to be high