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AMC1336: DSD to Full scale

Russell Perry
Prodigy 20 points

Part Number: AMC1336

Hi,

Im using the AMC 1336 with  ±1-V input range. I have the clock and dout connected to a Sigma Delta Filter module and I'm having trouble reading a full scale voltage.

Im injecting a 1 Vpp , 1 Hz, 0V offset sine wave and the largest value I read is 0.8 Volts.

My understanding of how to calculate volts:

DOSR  = 32. Filter = Sinc3

Meaning that Vout = dsd result * (1.0 / 2^15) 

Meaning that at 1 volt I would have  32768 * (1.0 / 2^15)

Can I get confirmation that my understanding is correct of how to convert counts to a voltage reading ?

  • +1
    TI__Mastermind 31655 points

    Hi Russell,

    An important thing to note is that applying a full scale input of +/-1 V will not actually result in all zeros or all ones in the bitstream. At +1V there will be a bitstream of 90% ones, and at -1V the output is a bistream of 90% zeros. With 16 bits of resolution, that percentage ideally corresponds to code 58982 (an unsigned code). Converting to signed, we just subtract 32768 to get a code of 26214, which is roughly 80% of 32678, and should account for your results.

    For details on the output bitstream of the AMC1336, please see the digital output section of the datasheet shown here:

    Regards,

    Scott

  • 0 in reply to Scott Cummins
    Prodigy 20 points

    Thanks! This explains my results!