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ADS1243-HT conversion rate?

Ron Evans
Prodigy 165 points
Other Parts Discussed in Thread: ADS1243-HT

I need some help figuring out the conversion rate I should be expecting from the ADS1243-HT.  I am clocking it at 1.25 MHz, 3.4V, DR0 DR1 = 00, SPEED = 0, gain = 1 or 16.  It seems that the datasheet indicates conversions should happen at 15 Hz, so one would take 67 ms.  For me, conversions are taking anywhere from 255 to 377 ms.  Does that sound reasonable, and do you have any suggestions on speeding this up?
Thanks
Ron

  • 0
    TI__Guru* 94075 points

    Ron,


    Based on the equation given on page 35 of the datasheet and on the setup information given, the data rate should be 7.629Hz. This data rate should be exact, since data comes out after an exact number of clock cycles for each conversions. With 7.629Hz, the data should come out every 131 ms.

    If you're measuring this with an oscilloscope (by checking the /DRDY line), it's possible your scope trace lacks the resolution (or is on a setting with too little resolution) to see each /DRDY pulse because the pulse is pretty narrow compared to the data period.


    Joseph Wu

  • 0 in reply to Joseph Wu
    Prodigy 165 points

    JW, you are right, I am now seeing DRDY go high every 131 ms.  I'm not sure what was going on before.  You "verified" your own answer, really?  What meaning does "verified" have when you can just verify your own answer?

    Ron

  • 0 in reply to Ron Evans
    TI__Guru* 94075 points

    Ron,


    I'm glad you were able to find a solution. If the resolution on the scope was the problem you were seeing, then great. I know I've seen this as problem when looking at the DRDY signals on some of our parts.

    Generally, if the question is not too complicated, I'll call it verified if there's been a suitable answer and if the original poster hasn't responded after a couple of weeks. Often people don't return to the post to verify an answer and I use it to track open threads. If there are future responses, I get emailed posts on the thread, and I can unverify the answer if need be.

    If you have any other questions let me know.


    Joseph Wu