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ADS7886: What is the format for SDO? What is the 12-bits of data representing?

Andrew Gras
Prodigy 10 points
Part Number: ADS7886


After digging through the datasheet I can't find a good description of what the output data bits are actually representing?

My guess is that the bits are representing some kind of GND to VDD scale for the input voltage, but I don't see that explicitly detailed anywhere. I'm hoping someone can give me more detail explaining what each output data frame is actually representing for a given input.

  • 0
    TI__Mastermind 22950 points

    Hi Andrew,

    The 12-bits of data on SDO represent the digitized input with VDD as the reference to the ADC. So essentially, the LSB is equivalent to VDD/(2^12). So you can back calculate the input voltage by CODE(in decimal) * LSB. 

    This device is a relatively straightforward device in that SDO just displays the conversion results as 12-bits of data. Note that there are 4 leading zeros so that should be taken into account when reading the data on SDO. I hope this helps and apologies for any confusion from the data sheet!

    Regards,
    Aaron Estrada

  • 0 in reply to Aaron Estrada
    Prodigy 10 points

    So using a random example 0000 . 0010 1110 1000 = 744 from the 12-bit binary data value (ignoring the 4 leading 0's) would result in the following calculation?

    (3.3/(2^12))*744 = 0.599V_in

  • 0 in reply to Andrew Gras
    TI__Mastermind 22950 points

    Hi Andrew,

    Yes, that is correct. Do you have the device on a board and seeing something different?

    Regards,

    Aaron Estrada