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How to debug ADS1230 Amplification

Jayaraj A
Prodigy 200 points

Other Parts Discussed in Thread: ADS1230

Dear All,

       Using ADS1230 for weighing scale; provided 22mV on input w.r.t to Gnd (single ended). DVDD,AVDD & reference+ are shorted and given to 5V and their grounds(ref-) are shorted. Gain & speed are also grounded. PDWN controlled through h/w circuit. The digital count coming out is nearby 9600 counts, only. Tried to debug on S/W side, but it is almost okay.(my gut feeling).

        22mV is provided through external power supply source, with the AIN- & GND shorted.

       Questions:

          1. If we give 22mV on input and monitor with DMM across Pin No 5 & 6(CAP) of ADS1230, what should be the voltage?

                          I am getting the same 22mV across pin 5 & 6. But the datasheet mentions, it is with a gain of 64.So I am expecting a voltage of 1.408V across those pins. But .it is not coming. I don't where I am missing.

              Kindly reply me.

  • 0
    TI__Guru** 113765 points

    Jayaraj,

    There are some conflicting statements in the datasheet about the input range.  We hope to resolve those conflicts as soon as we can.  Basically you cannot measure a unipolar input signal with the ADS1230 when it is referenced to ground.  The PGA of the device restricts the input within a specific common mode input range.  On page 3 of the datasheet is the common mode input range spec.

     

    So, basically you need to have the inputs at least 1.5V  from the supply rails.  So for testing purposes, if you build a wheatstone bridge so that the output is around mid supply and adjust one of the legs so that you get your 22mV difference, then you should get back the proper results.

    Best regards,

    Bob B