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RF430FRL152H: Resistive Sensor Bias Interface

Dennis Rosser52
Prodigy 10 points

Part Number: RF430FRL152H

I am in the process of designing a Bio-Medical circuit using the RF430FRL152H. In the RF430FRL152H, there is a "Resistive Sensor Bias Interface.” I would like to know the upper and lower resistance limitations for this device, or be directed to a location or PDF where I may find this information. Thank you kindly in advance for your assistance in acquiring this information.

  • 0
    TI__Expert 7820 points
    There is no max min limit on the for the "Resistive Sensor Bias Interface". The device will handle small and great resistances. It simply outputs a 2.4uA current (on TEMP1/TEMP2) which creates voltage on the resistor, which is then measured by the ADC.

    Check the datasheet on the current output range for TEMP1/TEMP2 at this section: Thermistor Bias Generator (5.24)

    Yes if you choose too great of a thermistor, the ADC will max out. Too small of a resistor and you may not be getting the best resolution. Using the PGA here would help.

    You should determine on your own which resistance values are suitable in your application.
  • 0
    TI__Expert 7820 points

    Some calculations for the maximum value:

    0.9V - reference for ADC

    3uA - maximum constant current output

    0.9V/3uA = 300kOhm which gives the maximum resistance that can be measured by the ADC before hitting the upper rail

    Using the PGA these are the maximum resistances,

    2x gain = 150kOhm

    4x gain = 75kOhm

    8x gain = 37.5kOhm