AD7091R-8 ADC conversion result

Hello AD,

I'm working on AD7091R-8 evaluation board.

Currently I have enabled 3 channels out of 8.

I'm using the channel sequencer for reading the conversion results.

When I'm  reading the conversion result of the enabled channels,I'm getting the channel ID correct but data is being read wrong.

Can you suggest some methods to debug this problem

Thanks,

Jayant

  • Hello AD,

    There is update regarding Conversion result read from the channels.

    When there is a delay of 2ms between read, then the conversion result is being read correctly from all the three channels.

    But when there is no delay, then result is not being read correctly.

    Please help with the problem.

    Thanks,

    Jayant 

  • 0
    •  Analog Employees 
    on Nov 26, 2018 2:39 AM in reply to jayant

    Hi,

        How did the mux_out pin connected? Was there any filter between mux_out and ADC_In pin? filter between these pins may cause delay in settling the input voltage and this also cause cross talk. If you can share your schematic, it would be helpful in analyzing the problem.

    Regards,

    Jonathan

  • Hi,

    I am using the evaluation board AD7091R-8.

    The schematics is available online(EVAL-AD7091R-2_AD7091R-4_AD7091R-8SDZ_UG-633),you can download it.

    As per the schematics,the LK13 & LK14 are connected through A between mux_out & adc_in which brings AD8031 in the picture.

    I also tried connecting LK13 & LK14 through C position,but the conversion results are not correct.

    If delay between each sample read is 2.5ms,then results are correct.

    If delay is less than 2.5ms,the sample values are not correct.

    Input to channels is given from the tap points Vin0,Vin1 & Vin2.

    Input tap points are isolated from circuitry consisting of AD8032ARZ by removing resisitors SL2,SL3,SL5 for Vin0,Vin1 & Vin2 respectively.

    SPI frequency is 1MHz.

    Channel register is written with 0x0007 for 3 channels sampling

    Tried multiple channel  write also,but unsuccessful.Conversion results were not correct

    How should I configure the Configuration register,what value should be written in it? 

    Any other methods to enable 3 channels of the AD7091R-8 & read correct conversion data from the ADC using SPI driver using channel sequencer?