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ADS8422 bipolar to differential input

sameer arora1
Prodigy 60 points
Other Parts Discussed in Thread: THS4131

 Hello,

         I am converting my bipolar signal to differential signals by THS4131 as shown in the figure 29 on page 16 of the data sheet, but when I read the signal on the PC, I cannot reconstruct the signal, it hits the rails of the ADC. Below Figure explains the problem.

thanks for ur help.

Regards

Sameer

  • 0
    TI__Expert 5705 points

    Hi Sameer,

    It looks like you are interpreting the ADC output as an unsigned integer. The ADC provides a signed integer output in 2's complement format that will lie in the range -32768 to 32767 (see Table 1 on page 20 of the datasheet).

    You can fix your output by shifting each code in your unsigned output set that is >= 32768 by -65536 to get the equivalent signed integer. In other words,

    for each code in your_set_of_unsigned_integer_outputs {

    if (code >= 32768) { code = code - 65536 }

    }

    I hope this helps.

    Best Regards,

    Harsha

     

  • 0 in reply to Harsha Munikoti
    Prodigy 60 points

    Thanks for your help, but I want to transfer only unsigned numbers ... 

    Regards

    Sameer

  • 0 in reply to Harsha Munikoti
    Prodigy 60 points

    Hello,

             My ADC DB9 and DB10 which are going to the microcontroller are sending data bits on 3V line when not connected to the controller but as I connect them to the microcontroller they go to 1V. I am using them as a 8 bit bus.

    Thanks