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ADC32RF45 Thermal Considerations

Dan Van Winkle
Intellectual 320 points
Other Parts Discussed in Thread: ADC32RF45

I've been evaluating the ADC32RF45 EVM for a while now.  About a month ago I noticed a drop in performance when I had left the board on overnight, and when I felt the ADC chip itself, it was too hot to touch.  I'm not sure how hot it was when it seemed to be operating normally, so I'm not sure if something has failed or if it's always run this hot.  I'm now in layout with this part and wanted to revisit the thermal requirements for this part.  I notice the EVM has a small heatsink soldered on the backside where the thermal pad is, but that the datasheet says nothing about this (that I could find).  Does this part require a heatsink, and does it have to be on the backside as it is on the EVM (or is the part thermally connected to the top of the package as well).   

How hot should this part be in normal operation, and do I need to be pointing a fan at it when running the eval board?

Thanks in advance.

  • 0
    TI__Mastermind 29220 points

    Hi,

    Given the thermal parameters of the device as shown in the datasheet (theta JA, JC, etc) and the power dissipation expected at your datarate and mode of operation, you may need a heatsink in your system.  It would possibly depend on how well your design is able to pull heat out away from the bottom of the device and spread it away.   At max sample rate and all the logic operating, the device does dissipate a lot of power.  So whatever you need to do to carry the heat away from the device, you would need to do.   The package does have the exposed thermal pad on the bottom of the package that is to solder to the PCB, so the primary flow of heat would be from the device downward into the PCB.   From there, heat would flow outward through the ground planes and could be dissipated out through the top of the PCB or out the bottom.   If there were other devices in the area of the ADC that also dissipated a lot of power then that would make it harder yet to carry the heat away.

    The EVM is not meant to be a production design, and sitting on a table top with no chassis and not much mass for the heat to go into, yes the EVM could benefit from a table top fan.   We will sometimes have a little USB-powered fan on the lab bench by the EVM, but not always.   We *are* looking to put a larger heatsink on the next revision of the EVM that would come with a small board-mounted fan for the ADC, much like the FPGA has on the TSW14J56 capture card, but still on the bottom of the board under the thermal pad of the ADC.   On the EVM we have the room for it on the bottom, but not all PCB enclosures would have clearance on the bottom side, so top side would work also but not be as efficient.

    Regards,

    Richard P.

  • 0
    Prodigy 170 points
    Dan, we are also using the ADC32RF45 EVM for performance testing and software development while our custom board is being designed. And we also noticed that the ADC gets quite hot. Our mechanical/thermal engineers have included heat dissipation in our custom board. In the meantime, as the main guy doing hardware/software testing using the EVM, I make sure I do not leave the power on when I am not there in person. It is a little inconvenient at times, but I would rather not risk heat induced damage to the chip or EVM. I will add a small fan as Richard suggests.