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ADS1131: Using A/D converter with 3 load cells in parallel

user275052
Prodigy 100 points
Part Number: ADS1131

I am using the ADS1131 in a design with a load cell that has an input resistance of 404 ohms. 

The excitation switch in the device is spec'ed to handle 30ma. 

I have a customer who wants to use 3 load cells in parallel. 

Excitation voltage is 3.3 volts which brings the current to 25ma.  

Is it a problem to bring the current this close to the spec?

Patrick

  • 0
    TI__Guru** 112765 points
    Hi Patrick,

    30mA is the rating over temperature, so 25mA will not be an issue as long as the load cell resistance remains relatively constant. I would suggest looking into the variation from load cell to load cell as there is bound to be some tolerance. The same would be true for the supply voltage regulation, so you would want to make sure that with all variables you do not exceed 30mA total.

    Best regards,
    Bob B
  • 0 in reply to Bob Benjamin
    Prodigy 100 points
    Bob,
    Thank you,
    Do you know if there is a current limit feature in the chip, or will exceeding the current damage the IC... not clear in the spec.
    Patrick
  • 0 in reply to user275052
    TI__Guru** 112765 points
    Hi Patrick,

    This is more or less an open drain FET circuit. There is some overhead built into the design, but no current limit for circuit protection. I would suggest keeping the current at 30mA or less.

    Best regards,
    Bob B