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Why LM73 temperature is wrong?

Seasat Liu
Intellectual 1040 points
Other Parts Discussed in Thread: LM73

All

My CTm use LM73.

They find temperature of LM73 will wrong one time after several thounsand time read.But the other registers is still right when read the wrong temperature.

Who can help me?

  • 0
    TI__Mastermind 33730 points

    Hi Seasat,

    In order for me to understand the customer setup, I would like the customer to provide detail on the following questions. Since the customer was able to read the register, this confirms that the I2C interface is working OK.

    1. How many parts do you see in this circumstance?
    2. Does this happens immediately after power up or does the part just start reading incorrectly after being powered up for a while?
    3. At what temperature does this happen?
    4. What is the power supply voltage being used? Please share a schematic with us.
    5. Does the value get stuck at a particular temperature or is it just reading an inacurate value?
    6. Before you power down the device, could the customer provide us the snapshot of the I2C communication when the customer reads the failed temperature?

    Aaron Heng

  • 0 in reply to Aaron Heng
    Prodigy 60 points

    Very old thread but I have the same problem. The reading changes from around 35 degrees C to sometimes first -40 and then after a few more seconds it changes to around 220 degrees or -220.

    1. I have one sensor connected

    2. After a while, seconds or minutes, sometimes not at all

    3. Happens at around 30-35 degrees for me, but I am unsure the temperature has anything to do with it. If the error has happened, cooling the sensor does not help.

    4. I have a 3V3 power supply for the temperature sensor. Im using a TLV62130ARGTT.

    5. The temperature keeps changing even after the bad readings start. So cooling the temperature sensor after fail makes the temperature reading go down. But from 220 and down.

    6. I have to set up the measurements again to get the waveform. Ill get back about that.

    To get the sensor reading correct again, it is not enough to redo the settings in the sensor and not enough to reboot the uC controlling it. It has to be power cycled.

    Thanks for any help!

    /Anders

  • 0 in reply to Anders Engman
    TI__Mastermind 33730 points
    Hi Anders,

    Thank you for reaching to us. Could you please capture the waveform for the power supply ramp rate? I know this might hard to capture, but hope that you can provide scope photo when the device behaves unusual at -40°C or other value.

    Aaron