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TMS320F28377S: TMS320F28377S How to measure a DC Voltage with 16-Bit Resolution

Part Number: TMS320F28377S

Dear all,

We are currently measuring a DC voltage with a voltage divider. We have very high requirements regarding the accuracy of this measurement, therefore we would like to use the 16-Bit Resolution instead of the 12-Bit Resolution. According to the datasheet and the technical reference manual of the TMS320F28377S, the 16-Bit configuration is only available in differential signal mode. Are there any issues if the ADC is connected as suggested in the first image? Is the expected performance with this electric circuit as indicated in the datasheet (gain and offset error)? Is it absolutely necessary to route the reference potential of the voltage divider in parallel to the output signal and connect them to the ADC as suggested in the second image? What is the best method to measure the output of a voltage divider in differential signal mode?

Thank you very much in advance for your advice.

Best regards

  • Hi Nicole,

    The voltage divider configuration in your figure will not work unfortunately for 16-bit differential.  (ADCINxP + ADCNxN)/2 should always be equal to the common mode voltage VREFCM.  VREFCM has to meet (VREFHI + VREFLO)/2 +/- 50mV to guarantee proper ADC conversions in 16-bit mode.  With the above voltage divider circuit, ADCINxN is essentially at AGND (0v) at all times so it will never meet VREFCM criteria.

    If your system requirement is really high that you need the 16-bit resolution, you should consider adding a single-ended to differential input buffer stage.  The single-ended to differential buffer will accept the voltage divider input and will generate the proper ADCINxP and ADCINxN levels that will meet the common mode voltage criteria.

    Hope this helps.

    Regards,

    Joseph