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Original question:

LMT87-Q1: accuracy at 150C

LMT87-Q1: measurement accuracy for temperatures up to 100 °C

Dennis Hagen
Prodigy 10 points
Part Number: LMT87-Q1

Hi,

What is the expected sensor accuracy, given that it is supplied with a stable supply voltage (5.0 V -+0.1 V), and a temperature range between -40 °C and 100 °C?

to break down the problem:

temp. -50 °C to 40 °C

From the table below I understand that the typical accurary is +- 0.3 °C at different values from this range. Can I assume that this accuracy is the min/max accuracy since the supply voltage is stable (the yellow lines in the table below)?

temp. 40 °C to 100 °C

I assume that at high temperatures (150 °C) the accuracy is low (+-2.7 °C according to the first line in the table below) What is the accuracy for temperature up to 100 °C?

  • 0
    TI__Expert 3595 points

    Hi Dennis,

    Over the full range described, you can expect a typical temperature accuracy of ±0.4 °C and a max error of ±2.7 °C. Our min and max specs are there to guarantee 6-sigma quality from production. This pertains to process and fabrication variation (assuming stable supply). Since 100 °C is within the 70 °C to 150 °C range, these same specs are expected. 

    May I ask what your key spec requirements are? We have a variety of analog temp sensors for different end applications that may better fit your needs.

    Best regards,

    Simon Rojas

  • 0 in reply to Simon Rojas Avila
    Prodigy 10 points

    Hi Simon,

    Thank you for your answer. We use the sensor in standard automotive applications. For example, in this case the sensor is used in  a motor drive unit to measure the PCB temperture. The analog output signal is digitized by the low-accuracy internal ADC of the microcontroller to lower cost. Hence, the total accuracy of the measurement is relatively low and we are trying to improve it without largely increasing either the complexity of the circuit or the cost. The maximum expected temperature is 100 °C. Do you recommend using a different sensor?

    Best regards,

    Ala Qawasmi

  • 0 in reply to Dennis Hagen
    TI__Expert 3595 points

    Hi Ala,

    Thank you for sharing these details. Since your main concerns are maximizing accuracy while using an integrated ADC I would recommend looking at TMP236-Q1. This analog temperature sensor offers a max temp accuracy of ±2.5 °C accross the full range and it also features a higher gain of 19.5 mV/°C. With these specs you can achieve higher accuracy and resolution using the same ADC--specially when using integrated ADCs that are typically delta-sigma with 12-bits of resolution. The main differences to consider are: the bigger DBZ package and a positive gain slope rather than a negative one--this can be easily handled in SW. 

    I also think it is worth mentioning TI's new self-integrated isolation analog temperature sensor--ISOTMP35. Which may be of interest for high-voltage automotive applications.

    Best regards,

    Simon Rojas