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TMP117: Thermocouples, CJC and Design Considerations

Darren (FAE)
Expert 5483 points
Part Number: TMP117
Other Parts Discussed in Thread: TMP116, TIDA-010019

I have a customer asking about the proper layout techniques to minimize errors when using the TMP116 / TMP117 type sensor for CJC in an enclosed, sealed case.

TIDA-010019 has some good pointers on positioning/layout, but the customer is very nervous about getting the required performance w/ these devices. 

Proper thermally rated screw terminal, placing the devices as close to the solder joint as possible...any other PCB layout techniques (islanding, vias, etc) or schematic level mods that need to be done to maximum performance and minimize temperature offset error from the isolation block to the device in a sealed environment w/ ambient temperature from MCU / device heating?

  • 0
    TI__Mastermind 41375 points

    Hi Darren,

    When it comes to thermal design, you want to minimize the thermal path to the object you're measuring while limiting thermal conductance to all other heat sources. 

    If the case is sealed, there should not be much thermal gradient inside except for high-consumption devices included in the design. Use distance, cut-outs and remove copper pour to limit thermal transfer through the PCB. 

    Copper pours and vias add metal to the PCB which can help thermal transfer from an object contacting them when they are tied to our sensor. They also add mass, which can increase thermal stability and increase thermal settling/reaction time. 

    If the CJC terminal block can sit on top of our sensor and/or be connected by thermal pastes/epoxies, this is best case scenario. If this thermal path is chosen, through the top of our sensor, eliminate all other thermal paths through the PCB as mentioned above. 

    thanks,

    ren