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Lowest Power Consumption Temperature Measurement Solution for RTD Temperature sensor

tae-kyeong um
Prodigy 10 points

Other Parts Discussed in Thread: ADS1120, ADS1220, ADCPRO, ADS1220EVM

Could you please introduce the lowest power consumption temperature measurement solution for RTD temperature sensor ?

In addition, as the recommended solution, we request the average power consumption when measuring the temperature once per second for the following design requirements. (Including power consumption by RTD excitation current)

* Design Requirements

- Supply voltage : 3.3V

- RTD type : 3-wire Pt100

- RTD excitation current : 1mA

- Temperature measurement range : 0'C ~ 300'C

- Resolution :  > 12 Bits 

  • 0
    TI__Guru* 91336 points

    Dear Tae-Kyeong - 

    Welcome to E2E and thanks for posting. TI does not make RTD's. We make semiconductor based parts which consume less current, are faster and can be more accurate than RTD. However - we do not make devices which can go up to 300°C - is this a hard requirement for your application?

  • 0 in reply to Josh Wyatt
    TI__Guru 59551 points

    Hi Tae-Kyeong,

    We have many ADCs that can interface directly with an RTD. I would look at the ADS1120 as a good, low power solution. In fact, the ADS1120 has a 3-Wire RTD Measurement solution shown in the datasheet in section 9.2.2.

    The ADS1120 is a 16-bit, 4-Ch delta-sigma ADC that can sample up to 2 kSPS and includes 2x current DACs (IDACs) for RTD biasing. Also, the ADS1120 can operate at 3.3V and consumes 605 uA of current (typ) in normal mode at 20 SPS with both IDACs on and the PGA enabled up to a gain of 16. However, since you only need to take one measurement every 1 second, the ADS1120 also has a powerdown mode that only consumes 0.4 uA of current (typ). So that means you will only be consuming 605uA for 5% of the total measurement time, and 0.4uA for 95% of the measurement time. Please see page 8 in the datasheet for more information on the ADS1120 power consumption.

    We also have an RTD cookbook that offers lots of useful information and circuit configurations for the different RTD types: https://www.ti.com/lit/an/sbaa275/sbaa275.pdf

    Let me know if you have any questions about this device.

    -Bryan

  • 0 in reply to Bryan Lizon86
    Prodigy 10 points

    Hi Bryan

    It would be appreciated if you could tell us the average current consumption including the excitation current of the RTD sensor.

    (Perhaps 605 uA is a current value that does not take into account the excitation current for the RTD sensor.)

    -Tae-Kyeong

  • 0 in reply to tae-kyeong um
    TI__Guru 59551 points

    Hi Tae-Kyeong,

    The ADC power consumption is listed in the ADS1120 datasheet as described. If you are looking for a system-level power consumption, I will leave it to you to figure that out for your specific system.

    Or, it might be beneficial to build a prototype so you can measure the actual current consumption seen by the system under your specific set of conditions. You should be able to hook up a 3-wire RTD using the J4 header on the ADS1220EVM. You can use the application diagram shown in the ADS1220 datasheet for reference. If you want to connect a different MCU to control the ADS1220 instead of using the ADCPro software, you can access the SPI signals via J10.

    I will also point you to our library of RTD linearization firmware that includes the RTD look-up tables in order to be able to determine the RTD temperature from the ADC output code. We are in the process of updating this software library to include the ADS1120 / ADS1220: https://www.ti.com/tool/ADC-TEMP-SENSOR-FW

    -Bryan