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CC2538: Temperature Sensor Inaccuracy

ikon
Genius 5355 points
Part Number: CC2538
Other Parts Discussed in Thread: TIMAC

Hi Support,

Found that the temperature sensor in CC2538 was inaccurate.
I believe this inaccuracy is influence by certain parameter but I wasn’t sure what could have influence it.

In our configuration, the ADC is using internal reference and we did a calibration at a fixed temperature by adding the different back from the value we capture from ADC.
The hardware consist of top PCB which contain the CC2538 and the bottom PCB which will be the IO and power supply (battery).
So the calibration for the top PCB was done with the bottom PCB connected to my bugger with a fixed voltage of 3.3V.
The same bottom PCB will be used for all the top PCB for calibration.

However, when the top PCB were attached to other bottom PCB after the calibration, it will still give out an inaccurate temperature value.
So what could have affect the CC2538 giving inaccurate temperature value?
Could it be due to different voltage where the bottom PCB was power by battery (around 2.6V) and calibration was done on 3.3V?
However, since we are using internal reference, I believe the supply voltage shouldn’t have any effect.
Can you please help me out on this?

Thanks.

  • 0
    TI__Mastermind 36395 points

    ikon, 

    You did not disclose any values about what you have measured, here is what the datasheet says about the accuracy of the CC2538 temperature sensor. How does it compare.

    Regards,
    /TA

     

  • 0 in reply to TA12012
    Genius 5355 points

    Hi TA,

    The things I observed is that when the same device was put back in bottom PCB which is use for calibration, it gives more accurate result.
    Anyway, with 1 point calibration, there is device that giving temperature of 22 deg C when the room temperature is about 28 deg C.
    This is only happen after I put it on the different bottom PCB than the one use to calibrate.

    By the way, I would like to have encryption on the association request and association response using TIMAC.
    Using the MSA example project from TIMAC, I am able to encrypt DATA frame type and devices can communicate well with encrypted data.
    However, when I try to encrypt the association request and association response, the device are not able to response to the encrypted data.
    I have posted but no reply yet: https://e2e.ti.com/support/wireless_connectivity/zigbee_6lowpan_802-15-4_mac/f/158/t/600342

    Thanks.

  • 0 in reply to ikon
    Genius 5355 points

    Hi TA,

    Any feedback?

    Thanks.