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We use a couple of LTM4667/LTM4677 for our board which we want to cool with liquid.

We use a couple of LTM4667/LTM4677 for our board which we want to cool with liquid. Is it better to cool it though the PCB instead of the top? In the data sheet the thermal resistance looks still smaller on the bottom. Our proto board shows cooling through the bottom works fine, but if we can improve it we might place it on the top.

  • On behalf of Anthony (Tony) Armstrong:
    You are correct in this understanding. Our micromodule regulators are adept at taking heat out through the top of the device as well as the bottom of the device. Each device type will vary depending on its internal construction and use of built-in heat sinks, but a “reasonable” rule of thumb is 55% though the bottom of the device and 45% through the top. As stated, this will depend on the product and its output current range and construction, so please read the data sheet for more specific data, we have spent a lot of time doing thermal characterization on each package.
    That said, you can always enhance a micromodule regulators thermal performance with additional enhancements such as heatsinks, air flow and liquid cooling techniques.