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TMP126-Q1: Part not working to 175C as specified in the data sheet

Mark Feydo
Prodigy 10 points
Part Number: TMP126-Q1

Hi,

   I have connected the TMP126-Q1 to my development system and am testing it.  Everything is working as expected at ~room temperature.  Today I put the sensor in a industrial oven to check it's operation at high temperature.  The over is set to 150 degrees C (and I have verified this is the actual temperature using a Fluke Temperature meter with thermocouple attached).  In the first several readings after inserting your device in to the oven I see the temperature rising and then the temperature reading from the chip drops to a very low value (0x0080 and 0x00CC seem to be most common).  If I then remove the chip from the oven it "recovers" and I can watch the temperature fall back to room temperature.

   I have tried with two devices and both are behaving exactly the same.  My system is setup to take one reading every 20 seconds.  The highest temperature I have seen is 114C and by the next reading the low value reading is present.

   So, a couple questions:

1) Does the device really work to 175C as stated in the datasheet?  Is there anything special I need to do to get it to work at maximum temperature?

2) What is the expected behavior of the part when the temperature exceeds 175C?  Is there any way to know if I have went above the temp limit of the chip?

3) I see this part is now out of stock.  Any idea when more will be available  ...  should I continue to plan on using it in my soon to be released product or is it many months / years away?

Thanks,

mark

  • 0
    TI__Guru* 91206 points

    Dear Mark -

    Thanks for the post and welcome to E2E! 

    Which variant of the PTMP126-Q1 are you using? I assume the DBV version, as the DCK is in stock, but wanted to check that with you.  

    With regards to your testing, if you can provide any images of your setup or connection diagrams, that would be most helpful to assist us in finding root cause for you - these devices are pre-production (the P marking indicates that) but multiple lots of units have undergone high temp testing that we do as part of our qualification and passed  - so here it might be some other component that is failing at the high temperature - therefore as much detail about your setup you can share would be great. The abs max on the junction temp of the device is 180C, so if you only went to 150C, you should not have exceeded it.

    Regarding the release to production for this device - currently we are on schedule to release the -DBV (if that is the device you are using) in early Q1 of 2022, -DCK will come some months after that. 

  • 0 in reply to Josh Wyatt
    Prodigy 10 points

    Hi Josh,

       I am using the DBV version of the part.  My setup is pretty simple  ...  I have a small board with my microcontroller, an LED and a 5 pin connector for the cable going to the TMP126-Q1.  The TMP126-Q1 is mounted on a small prototype board to which the other end of the cable is connected.  There are no other components on the board with the TMP126-Q1.  The cable between the boards is about 6 feet in length.  Only the TMP126-Q1 and about 1 foot of cable are inserted in to the oven during the test (the microcontroller board and remainder of the cable are outside of the oven).

    I don't seem to be able to insert / paste any pictures or drawings here  ...  do you have an e-mail where I can send them to you (or a tip on how to insert here).

    Thanks,

    mark

  • 0 in reply to Mark Feydo
    TI__Guru* 91206 points

    Mark - 

    Thanks for the explanation - here you are running SPI bus over a long distance - I personally noticed issues above 4MHz with six inch lengths of wire which were not twisted or shielded. You may check and then reduce your SPI clock frequency (I tested 16MHz to 125kHz) to see if that helps you out and also monitor the actual SPI bus with a logic analyzer or o'scope to see if the heat is affecting the measurement return in any way and also double check your wire and the PCB are rated for this temp. 

     When you reply to insert your images, you should see a toolbar on the bottom, choose Insert, then Image/Video file. 

  • 0 in reply to Josh Wyatt
    Prodigy 10 points

    Hi Josh,

       I am running the SPI clock at 4.1kHz (very slow), so I don't expect the cable length is an issue.  I also used an oscilloscope to verify the CLK, nCS and MOSI / MISO signals.  The all look good at both room temperature and at higher temperatures.

       In my most recent tests I saw the same problem as before (bad readings in the 100 - 120C range), but this time the part started to work again at about 120C and worked up to 155C before it once again gave bad values as I ramped the oven up to 165C.  I'm starting to wonder if it is a "thermal shock" issue  ...  as I move the part from room temperature into the over at 100C it immediately sees the big temperature change and then after some time soaking at this higher temperature it begins to work again.  My next test will be to put it in the oven at room temperature and slowly ramp the oven temperature from ~20C to the higher temperatures (unless you have a different suggestion).

    Thanks,
    Mark

  • 0 in reply to Mark Feydo
    TI__Genius 9675 points

    Hi Mark,

    Can you please send images of the scope captures in reference? Also, what type of cabling are you using in your test set up?

    Jalen