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ADS1263: STATUS byte is showing incorrect clock source

Prodigy 30 points

Replies: 2

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Part Number: ADS1263

Hello,

I am testing the ADS1263 for some new instruments and have a strange problem.

At the moment i have 2 different boards using the ADS1263

One is using the ADS1263 with an +2.5V and -2.5V analog supply and  that is working ok.

The other is using a +5V analog supply and here the A/D conversion is not working correctly

I can program the ADS1263 without problem but when i read the data from the conversion register

i get an status back of 0x64 wich indicates that the ADS1263 is using an external clock but pin 15 is connected to ground

so it should be using the internal clock , the other board works that way without a problem.

Since the oscillator is not selectable via the registers my conclusion was that the chip was defective so i replaced it.

That did not solve the problem , the new chip also thinks it is using an external oscillator.

So i can't figure out what causes this problem.

The only thing i see is that both working boards have a ADS1263 with different codes on the housing as the board that does not work.

So it might be that i have some bad chips but that is unusual for new chips that were in a strip that was cut form a reel by Farnell

Any suggestions for other possible causes ??

Kind regards

Ed van Rijn

  • Hi Ed,

    Welcome to the TI E2E Forums!

    Do you happen to have a schematic of the ADS1263 in your problematic circuit that you could share?

    I am currently wondering how you have the ADC grounds connected...Do AVSS and DGND connect together when you supply the analog supply on the ADS1263 from 5V? If there is ground bounce on the CLKIN pin it might be able to trigger the external clock detect circuit. However, what doesn't make sense to me is how the ADC would continue to function if no external clock was being provided.

    So another question, is it possible that the 0x64 byte is actually a part of the data, and not the STATUS byte value?

    Best regards,
    Chris

    Best regards,
    Chris Hall
    Applications Engineer | Precision ADCs


    Check out these helpful resources...
    TI Precision Data Converters | TI Precision Labs - ADCs | Analog Engineer's Calculator | Data Converters Learning Center | Selection Guide

     

  • In reply to Christopher Hall:

    Hello Chris,

    Thanks for your fast reply.

    Based upon your remarks and question i looked a the schematics and pcb layout.

    I copied a part of the schematic into this reply/

    Analog and digital ground are both connected to a common analog groundplane so they are connected together and

    since the analog groundplane is seperated from the digital groundplane there is no groundbounce problem, in fact

    the board layout is almost exactly like the layout in figure 163 of the datasheet.

    It turned out that i was fooled by an error in my firmware, the status printed on screen displayed 0x64 but shoul have been showing 0x40

    wich is of course 64 in decimal.

    I changed this and completed dome more firmware routines and now everything is working ok.

    Thanks for for your help.

    Kind regards,

    Ed van Rijn

    Tradinco Instruments

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