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ADS131A04EVM: In the delta sigma evaluation software, what Vref do you need

Sebahaddin Yilmazer
Prodigy 80 points
Part Number: ADS131A04EVM

I have been using Vref= 2.5 V but I am not sure if that is right to use. Also the conversion from the code to voltage output is: Code * (FSR/(2^24)) or is it different ?

Best regards,

Sebahaddin Yilmazer

  • 0
    TI__Guru 57366 points

    Hello Sebahaddin,

    Thank you for your post.

    You may use the internal 4-V reference voltage if AVDD - AVSS > 4.5 V. The ADC output code conversions are listed in Tables 8 and 9. You must also remember to divide the full-scale range (FSR) by the gain setting used.

    Regards,

    Ryan

  • 0 in reply to Ryan Andrews
    Prodigy 80 points

    Hello Ryan,

    I am using the negative charging pump to allow voltages to -1.5V for measuring current transformers. Because of this I have to place the jumper on pin 1 and 2 of JP11, this will result in a single-supply configuration (3.3 V to AVDD and AGND to AVSS). So probably I can only set the VREFP to 2.442 V. If I combine this with external reference voltage (INT_REFEN), what Vref do I need to use when using the data analysis ? When I am using Vref=2.5 V in the data analysis, the pk-pk code value converted to analog voltage is pretty accurate. Using Vref=2.442 will give me less accurate results. Also do I need to change the INT_REFEN to internal reference voltage enabled or doesn't that affect the output. Also JP9 is installed by default.

    So for example I have chosen Vrefp = 2.442 V is this my Vref as EVM parameters and if so, the calculation to get analog output voltage using input signal of 20 mVpp:

    The pk-to-pk code is 67521, which will give us 67521 * ((2*2.442)/2^23) = 0.039312 V / 2 = 0.019656 V, which is 1.42% off the actual input value.

    Using Vref=2.5 V results in 67509 *((2*2.5)/2^23) = 0.0402385 V / 2 = 0.020119 V, which is 0.60% off the actual input value.

    Are there also some tips and tricks to get more precise output using ADS131A04EVM ?

    Regards,

    Sebahaddin