• State TI Thinks Resolved
  • Locked Locked
  • Replies 2 replies
  • Answers 1 answer
  • Subscribers 47 subscribers
  • Views 339 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

ADS1261: ADS1261

Ram Ch
Prodigy 120 points
Part Number: ADS1261

Hi Bryan,

Need your inputs in configuring the ADC external reference and INPMUX configuration.

we had a sensor connected to ADS1261 as shown below (you may be knowing from the earlier conversations)

Here Vref is 2.5V and  X,Y and Z are outputs(range is 0 to 4V). AIN0 and AIN1 are configured for external reference, AIN2-AIN3 for measuring X, AIN4-AIN5 for measuring Y and AIN6-AIN7 for measuring Z.

Below are my questions.

1) In place of AIN1, we would like to set AVSS internal (default) in negative input of REF register, so that AIN1 line can be eliminated. does AIN0-AVSS internal (default) configuration will work as external reference? 

2) we want to use common negative input configuration in INPMUX register for measuring X, Y and Z. That means AIN2-AIN0 for measuring X, AIN4-AIN0 for measuring Y and AIN6-AIN0 for measuring Z. This will eliminate AIN3, AIN5, AIN7 lines. Which is better? having common negative input vs separate negative inputs. Doing this will have any effect in ADC counts of X, Y and Z?

Please advise.

Thank you,

Ram.

  • 0
    TI__Guru 52296 points

    Hi Ram,

    If you are going to use an external reference input, I would use one of the complete pairs of inputs e.g. AIN0 and AIN1, as opposed to using AIN0 and then AVSS directly. Using the complete reference pair allows the differential reference voltage to follow the same path into the ADC. You want this voltage and connection to be as clean as symmetrical as possible, since it is the basis for all other measurements on your board. However, I will say that I have not tried the configuration you are suggesting, so I cannot be sure that this is true (I am sure there is a dependency on the grounding and layout as well). This is more of a gut feeling based off of past experiences.

    Since the ADS1261 internal mux is fully flexible, you can measure against any combination of inputs. So if the negative channel (MUXN) will be the same voltage for each measurement - in this case, 2.5V - then you can absolutely tie this to one input e.g. AIN0 and then measure the other channels against AIN0. There is no drawback to doing it this way. In fact, it is probably better for your application because then you don't have to route VREF to multiple inputs, and you know each channel is always being measured against the same voltage.

    -Bryan

  • 0 in reply to Bryan Lizon86
    Prodigy 120 points

    Thank you very much, Bryan!