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TMP112: the temperature doesn't refresh even with temperature change

Frank Xiao
Genius 12055 points
Part Number: TMP112

Hi team,

my customer is using the TMP112 now, sometimes the temperature doesn't refresh even with temperature change. Do you have some ideas how to check more? Thanks.

  • 0
    TI__Guru* 90906 points

    Frank - 

    If possible, could you provide some more detail here? For example, logic/analog analyzer captures of the I2C bus and power rail - (to see the communications to and from are OK.) Board schematic and layout would also be helpful, along with a description of the test environment. (for example, is this observation done while in a chamber?, at what temp?, with some information on their reference that they are using to measure against) 

  • 0 in reply to Josh Wyatt
    TI__Guru* 90906 points

    Frank - 

    Thanks for emailing me the captures and the drawing - 

    I would say first they need to clean up the drawing as the connection points are not properly annotated. Also, the 1k pullup they put on VCC/VDD might reduce the input voltage to 3V, so now they have set up situation where the MCU I2C might be a 3.3V and the device is operating at 3V. This is not a good practice. They should just connect directly to VCC and get rid of the pullup resistor.

    Thirdly - they have a very noisy I2C bus, there is clearly something related going on with the power while the MCU is running the I2C - almost looks bit banged, so to me, at this point, i would say they are lucky it even works once. I would recommend they need to clean the ringing, the overshoots, undershoots, and the general noise on the rail)  - the entire schematic was not given and no layout was provided, so if they need help there, they will need to provide those details.

     

     

  • 0 in reply to Josh Wyatt
    TI__Guru* 90906 points

    Frank - 

    I have continued looking at this - 

    Here is a screenshot of one of the transactions you sent me. This looks to me like: 

    Start, 0x90 + ACK, 0x01+ACK, repeated start, 0x91 + ACK, 0x60+ACK, 0xA0 + NACK, Stop - only thing that jumps out here is the spike on the 0x60 byte, on the eighth bit, but the part ACKs that anyway. 

     

    Here below is an LSA capture that is working duplicate of what i think your customer is attempting. It does not show any noise of course, but it is same  

    So - please show me where it breaks. I did notice on that capture you sent, looks like I2C (if 100uSec per division is correct) means they are running the bus at about 10kHz - the part should be good down to one 1kHz, and wanted to confirm they did not try raising the bus speed yet.)