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Original question:

ADS1234: Minimum circuity to get it working

ADS1231: Design mistake in weight module

Federico blum
Prodigy 10 points
Other Parts Discussed in Thread: ADS1231

I designed and manufactured a weight module with ADS1231 IC and it's not working. I think I put a wrong capacitor (C7, part number: 04023C104KAT2A) in-between CAP pins. Also the capacitors between AINP1 and AINN1(C4) and VREFP and VREFN (C9) are wrong. I copied a circuit that works and these are the values it has, but in my design it doesn't work. Is there anything I can do to make this work? replace the caps? C7 is 0402, the cap i need is in 1210 package...
  • 0 in reply to Federico blum
    TI__Mastermind 47090 points

    Hello Federico,

    Welcome to the TI E2E community.

    Your schematic looks correct.  The input capacitors are very large, which may cause settling time issues, but should still work.  Capacitor C7 should be an NP0/C0G type, which will come in a 1210 or larger package.  However, this is only needed to meet datasheet performance; the ADS1231 should still work with a standard 100nF 0402 capacitor.

    When you say it does not work, are you able to get conversion readings that are incorrect, or do you not get any conversion results?

    If possible, please use an oscilloscope or logic analyzer and capture a full conversion from on SCLK and DRDY/DOUT pins, similar to Figure 19 in the datasheet.

    Also, what voltage are you using to excite your bridge sensor?  I assume 3.3V?  I do not see a connection to the 3.3V AVDD supply on your board to the bridge sensor, which is why I ask.

    Regards,
    Keith Nicholas
    Precision ADC Applications

  • 0 in reply to Keith Nicholas
    Prodigy 10 points

    Hello Keith! I shorted a cable between VCC and E+ and between GND and E- and it worked! Before that I was having 0Kg all the time as conversion result. I thought the reference was connected internally...