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ISO124: DESIGN SUPPORT

Gangula sravanthi
Prodigy 70 points
Part Number: ISO124
Other Parts Discussed in Thread: OPA2990, ISO224,

Hi Team,

I need you support  for new design.  requirement is taking potentio meter output to rc filter--->buffer opa2990 >> divider(1/8)---> ISO124U ---> ADC PIN OF MCU.

 

Supply voltage :

 potentio meter :24v

buffer:24v single ended,

iso124u: dual supply±5v.  my doubt is due to negative rails ,is mcu fails? is there any other ic for this adc measurement(linear voltage measurement). ADC.jpg

 

  • 0
    TI__Guru**** 181751 points

    Hi Gangula,

    Please take a look at the ISO224 instead.  It is a newer device compared to the ISO124 and the output does not go below ground.  It only needs 5V supplies so there is no need for dual +/- power rails.

  • 0 in reply to Tom Hendrick
    Prodigy 70 points

    Thank you for the reply..

    Dear Tom Hendrick,

    I was partially tested iso124u. input is ~0v,output is -17mV.  Please clear the doubt , is there any chance to get negative voltage on the output during power on?

    You are suggested iso224. this is good ic  but output range is 2.5v to 3.3v. difference is 0.8v (adc measuring range) .might be difficult to give the accuracy of moving plate in mm.

  • 0 in reply to Gangula sravanthi
    TI__Guru**** 181751 points

    How is U31 powered?  You need headroom on the ISO124 for both the input and output side.  The ISO224 output gain is 1/3, so you could potentially remove the divider on the input.

  • 0 in reply to Tom Hendrick
    Prodigy 70 points

    Dear Tom,

    Am giving 24vdc single ended power supply to U31. potentiometer-wiper output range is 0-24v.  am using STM controller with adc vref is 3.3v only. So i need the range 0-3v(safe). u31 output is same as input that is input 5v given and getting output 5v(buffer circuit) and  i applied  -1v to non-inverting terminal for R&D, i got Vout is mv (positive). input of iso124  is positive.

    input of iso124= 0v and output is -17mv i measured.  i explained  my circuit and have a doubt about negative voltage is coming at output or not? if any chance is there i will change the circuit diagram because now  am doing the  pcb design  .after sending of manufacturing not possible to update immediately. so please clear the doubt as early as possible. Thank you for your support.

  • 0 in reply to Gangula sravanthi
    TI__Guru**** 181751 points

    You could try differnt test conditions - maybe cycle -Vs before +Vs and see if that is going to have an impact on your output.