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ADS131M06: Differential inputs for ADS131M06

Deepak c
Prodigy 100 points
Part Number: ADS131M06
Other Parts Discussed in Thread: ADS131A04

Hi Ryan,

Can you please help me with connections for Differentail inputs for ADS131M06?

I want to measure Line voltages (L1,L2,L3 with respect to Neutral).

I have checked application Information where Neutral and AGND Shorted.

  • 0
    Prodigy 100 points

    Can you confirm whether we need to connect? 

    Neutral and AGND (ADC Analog GND)?

  • 0
    TI__Guru**** 176701 points

    Hi Deepak,

    Are you referring to Figure 9-5 in the ADS131M06 datasheet?  If I understand your diagram correctly, you want to break the connection from Neutral to the ADS131M06 and the high side of the isolator.  If my understanding is correct, then unfortunately that won't work as you need to make sure you stay within the common mode operating range of the ADC.

  • 0 in reply to Tom Hendrick
    Prodigy 100 points

    I have voltage divider at ADC Differential pins..from mains and limiting to 1.2V.. still we need to connect AGND and Neutral..

    In this case why single ended opamp will also work?

  • 0 in reply to Deepak c
    TI__Guru**** 176701 points

    Hi Deepak,

    Can you sketch up what you mean with the single ended op-amp?

  • 0 in reply to Tom Hendrick
    Prodigy 100 points

    Sorry.. i mean single ended ADC will work out

  • 0 in reply to Deepak c
    Prodigy 100 points

    Hi Tom,

    I have referred some of the design from ADC for Differential input sensing.

    Can you please let me difference from both the Diagram

    Left figure is single ended ADC (Neutral to connect to ADC GND?) If connected then it shall treat Live to neutral as single ended ADC.

    Right hand side (Voltage portion Calculate the Difference and giving to ADC) so i see that is differential.

    Can you please confirm on both which should be good.

    .  

  • +1 in reply to Deepak c
    TI__Guru**** 176701 points

    Hi Deepak,

    In both cases, the ADS131A04 is powered from a bipolar source, so on the left side you are measuring line (AINP) to Neutral (AINN).  Neutral is tied to AGND and you would see +/- signal on the AINP.  The right side is measuring voltage line-to-line with AGND tied to the center point of the two voltage divider networks.  Either circuit is valid depending on what you need to measure.

  • 0 in reply to Tom Hendrick
    Prodigy 100 points

    Hi Tom,

    Thanks For reply.

    Can you please help with Drawing for second cases for 3 PH voltage measurement (L1, L2, L3 wrt N).

    Max voltage shall be 277Vrms.