• State TI Thinks Resolved
  • Locked Locked
  • Replies 1 reply
  • Answers 1 answer
  • Subscribers 45 subscribers
  • Views 492 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

ADS1248: ads1248

shridhar hl92
Prodigy 10 points
Part Number: ADS1248

Hi Team ,

i have one query in my design , my design based on 2 wire Ratiometric RTD Measurement topology. in that how to read voltage across reference resistor in ADC.

means which register configuration need to make and where this read value will be stored.

  • 0
    TI__Guru** 113765 points

    Hi Shridhar,

    Welcome to the E2E forum! The returned code value of the RTD measurement is determined as ratio of the RTD resistance to the reference resistor.  The value of the RTD is: Rrtd = (conversion code returned / positive full-scale codes) * Rref.  For the ADS1248 the positive full scale is 8388607 (or 0x7FFFFF).  So the reference  voltage value is not important unless you are trying to check for a broken wire.

    You can use the System Monitor functionality for checking the value of the voltage reference.  The System Monitor is discussed in section 9.3.12 starting on page 35 of the ADS1248 datasheet.  In particular see section 9.3.12.2.  To use this function you will need to use the internal reference.  The value returned will be approximately 1/4 of the actual reference voltage value as a normal conversion result.

    The register changes required for this measurement are the appropriate settings for the VEFCON and REFSELT bits in the MUX1 register (page 59 in the datasheet) using the internal reference and the MUXCAL bits for the System Monitor (also the MUX1 register).  The MUXCAL settings would depend on which reference is being measured.

    Best regards,

    Bob B