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ADS830E output random data?! Why?

bear19
Prodigy 30 points

Hello everyone,

I am a chinese engineer, Recently, I want ADS830E to design a High speed Data acquire card.Now, I encountered a lot of problems about ADS830E. The output data of ADS830E board are all random datas. In fact, I acquired a lot of noise signals when i input a analog signal that was from a output pin of a MCU.I really don't know How to solve them. Who can help me?

Now,I, firstly, introduce my boards to you.

One is MCU board which may read I/O data of ADS830E output pins. The other is ADS830E data card.There is a only A/D IC on this board. The schematic of ADS830E data card is from ADS830E-EVK. However, There is a big difference between my ADS830E board and ADS830E-EVK. The difference is that my board has not AMP OPA681U for Input pin of ADS830E. My board work in single-ended mode.

I  directly want to input an analog signals that is a Output signal from a pin of MCU to input pin of ADS830E board that is my board. In here, The Output signal voltage from a pin of MCU is range from 0.0V to 3.3V. Accroding to the datasheet of ADS830E, the signals inputed range from 1.5V to 3.5V in single-ended mode, But my signals provided for input pins of my ADS830E board work range from 0.0V to 3.3V. Does i need a AMP OPA681U for my ADS830E board? I must install a AMP OPA681U on it??

Who can help me? Thank you for your any help.

Sincerely,Yours

Bear19

 

  • 0
    Prodigy 30 points

    Where is the Ti technical Support Engineer? Who could help me ?

  • 0 in reply to bear19
    TI__Mastermind 29220 points

    Hi,

     

    I have been looking into this issue for you.  Sorry for the delay in response.

    I can say that the input signal must be conditioned so that it is always between 1.5V to 3.5V, so having an input signal that can be from 0 to 3.3V will not work correctly.  But i would have expected this to simply cause an overrange issue and clip the lower portion of the signal rather than cause the output to look random.  So i would expect there might be other issues in the setup and i believe i need more information.  You may use an amplifier or some other method to scale your input signal and bias the level of the signal.   I don't know the nature of your input signal to know if simple AC coupling would be enough to let you bias the signal into the ADC to the proper common mode.  AC coupling (through either seried AC coupling caps or transformer) would not pass a DC level or very low frequency components so an amplifier would be needed if your signal needs to have DC or low frequency components preserved.

    May i ask for more information about your circuit diagram and a screenshot of what the random output data looks like?  If you don't wish to post these in a public forum you may email them to hs_converter_apps@list.ti.com and i will see them there.   Is there also a screenshot of what a typical input signal might look like?

    Regards,

    Richard Prentice

     

     

  • 0 in reply to Richard Prentice
    Prodigy 30 points

    I sended the mail to your mailbox. Thank you for your any help. Thanks.