• State Resolved
  • Locked Locked
  • Replies 3 replies
  • Answers 1 answer
  • Subscribers 45 subscribers
  • Views 552 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: IDAC accuracy specification questions

ttd
Mastermind 8610 points
Part Number: ADS1261

 

Dear Technical Support Team,

 

I have some questoins about IDAC specification of ADS1261.

 

①

Is it correct understanding about Accuracy and Same Current magnitude below?

 

The current spec of accuracy is ±4%. When both IDAC1 and IDAC2 are set 1000uA, , the max range is from 960uA～1040uA(Accuracy).

The difference between IDAC1 and IDAC2 is max ±1%, so when Idac1=1000uA, Idac2 may drift 1000uA±10uA(Same Current magnitude)

 

②

What the meaning of the "Different current magnitudes" ±1% on datasheet?

 

③

Does the ripple of AVDD affect "Match error" spec of IDAC ?

Datahsheet has "temperature vs Match error" like Figure 47 , however it doesn't have "drift of AVDD vs Match error".

So I'd like to confirm it.

 

Best Regards,

ttd

  • 0
    TI__Mastermind 44680 points

    Hi ttd,

    1. That is correct. Those current ranges are valid for the specified accuracy.
    2. I am not entirely sure why we needed to specify a matching specification for different IDAC currents. For simplicity, it is save to assume that both IDACs may have a 4% error in opposite directions; however, I think the point of this metric is to say that the two IDACs will tend to error in the same direction (i.e their errors are somewhat correlated). As it was explained to me, IDAC1 may have +0.5% and IDAC2 may have a -0.5% error, so when "added" together they will have a combined 1% matching error when set to different currents.

    3. I don't have any data on power supply rejection, as it related to the IDAC current; however, as long as the supply ripple does not put the IDAC compliance voltage out of spec, then the IDAC current magnitude should show very little sensitivity to the power supply voltage or power supply ripple.

     

  • 0 in reply to Christopher Hall
    Mastermind 8610 points

    Hi Chris Hall,

    Thank you for your reply.

    I have additional question about  "Different current magnitudes" .

    I draw a image of this. When IDAC1=500uA and IDAC2=1000uA, "Different current magnitudes" means ±1%(Typ) from the line of IDAC1 on 1000uA(Virtual reference) point?

    orotherwise, does the line of "Different current magnitudes(type±1)" be inside of  "same current magnitudes(Max ±1)"? 

    I'm happy if you confirm this to the developer of ADS1261 and check my drawing.

    ADS1261_IDAC.pptx

    Best Regards,

    ttd

  • 0 in reply to ttd
    TI__Mastermind 44680 points

    Hi ttd,

    I was able to find some characterization data on this. Hopefully this graph will help:

    Notice that the X-axis and the individual lines (of varying color) make up all combinations of IDAC current settings. Therefore, the vertical distribution of points at any point along the x-axis shows how one IDAC's current setting will affect the accuracy of the other IDAC.

    For the lowest current settings (50 and 100 uA) and even the 1.5 mA setting,  there is hardly any additional error based on how the other IDAC is configured. For all other IDAC settings, there seems to be an +/- 0.3 % error that may add to the initial error.