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ADS1282: Data format for unipolar power in Avdd and Vref for ADS1282

bugmenot bugmenot
Intellectual 285 points
Other Parts Discussed in Thread: ADS1282

Part number: ADS1282

Hello, I am planning to use the ADC1282 for a high precision measurement, the fact is that the signal to be measured is unipolar and I wonder how the output data is with this configuration. The bipolar configuration is:

Avdd = 2.5V

Avss = -2.5V

VrefP = 2.5V

VrefN = -2.5V

If I have understood the data sheet correctly, my data format will be:

Vref = VrefP-VrefN = 2.5 - (-2.5) = 5V

Vin_Max = Vref / 2 = 2.5V 7FFFFFFEh

Vin_Min = -Vref / 2 = -2.5V 80000001h

But I'm not clear about what the data format will be like for the unipolar configuration:

Avdd = 5V
Avss = 0
VrefP = 5V
VrefN = 0

Now, how will the data format be ????????????????????? and the format of imput ???????????

If the signal is unipolar, there is some way to use the 31 bits of the ADC without having to lose the sign bit (although I have to make masks in the code) ??????????????

Best regards.

  • 0
    TI__Guru**** 174921 points
    Hi Bugmenot!

    The output code from the ADS1282 will always be in binary two's complement format (see Table 13). When you go from a bipolar setup using +/-2.5 V to a uniploar setup using 0-5 V, you are essentially level shifting everything by adding an offset to your input signal. FS+ will be at still be 7FFFFFFFh, FS- will still be 80000000h, etc.
  • 0 in reply to Tom Hendrick
    Intellectual 285 points
    Thanks Tom,

    This means that my data will be:
    + FS = 5V Differential input 7FFFFFFFh
    0 = 2.5V Differential input 00000000h
    -FS = 0V Differential input 80000000h

    If this is the case, I can use masks (in the microcontroller code) so that my unipolar range is 0 to 5V.

    If this is not possible, what configuration do you recommend when the signal to be measured is unipolar?

    Best regards
  • 0 in reply to bugmenot bugmenot
    TI__Guru**** 174921 points
    Yes - that is correct! You can use the micro to change B2C to straight binary if you like. Have a great day and feel free to let us know if there is anything else we can help you with.