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UCD3138 ADC14 for temperature sensor

felix.he
Prodigy 120 points
Other Parts Discussed in Thread: UCD3138

Hi,after getting the ADC14 value of UCD3138 ,how to convert it to temperature value?

  • 0
    TI__Expert 4970 points

    Felix,

    Take a look at the Temperature Sensor section under the Electrical Characteristics table of the Datasheet. This gives you the Voltage Resolution (5.9mV/°C). It also shows the temp range is -40°C to 125°C which corresponds to a voltage range of 1.46V to 2.44V. Finally it mentions that there is a factory trimmed 25°C reading that is per device.

    Please reference section 4.20, and section 4.23 of the Datasheet, and sections 1.11, 1.12, 2.3, and 2.6 of the Monitoring and Communications Programmer's Manual.

    The factory trimmed 25°C reading is in the TEMP_REF register. So get the value in that register and convert it to a voltage: Vtrim = 2.5 * 4096 / TEMP_REF.

    Vtrim is the voltage measured for that device at 25°C.

    Likewise, take your temperature reading from the device and convert it to a voltage.

    From here you can use the straight line formula y = m * x + b, where m is the voltage resolution of 5.9mV/°C, and b is the y-intercept that you can calculate by using the point of Vtrim @ 25°C.

    Section 3.8 of the Datasheet describes the devices temperature performance characteristics.

    Please let me know if you have any more questions. Thanks!

    Regards,

    Brandon Vonk

     

  • 0 in reply to Brandon Vonk
    Prodigy 120 points

    Brandon Vonk,

    Thanks for your help and I get the correct temperature now.

    I met anther question on my UCD3138HSFB-029 today.The  output current of the calculation is wrong,so I want to know about the relationship between the resistance  and the temperature of the copper.Can you offer me some information?

    Best Regards,

    Felix

  • 0 in reply to felix.he
    TI__Genius 13700 points

    Copper's thermal coeff for resistance is 0.394% per degree C.

  • 0 in reply to Brad
    Prodigy 120 points

    Brad,

    Thanks,But what is the original resistance of the copper?

    Best Regards,

    Felix

  • 0 in reply to felix.he
    TI__Expert 4970 points

    Felix,

    The resistance of this copper trace is close to 0.5 mΩ. However, if you need more accuracy, you should perform a room temperature calibration to measure this resistance more accurately. We usually do this by taking a two point measurement of the output voltage and current, fitting these points to a line and extrapolating the slope (resistance), and the offset from there.

    Please let me know if you have any more questions here. Thanks!

    Regards,

    Brandon Vonk