# Nordic nRF52840 Thermal Characteristics

Hi Nordic,

I’m H/W engineer, dedicated in development of radio circuit. I ask the question because we’d like propose your Nordice nRF52840 to our customer when replying the request of a BLE radio. So far we check the solution with the capability, much higher transmitting power than our usual solution, so it looks good but we found it better to estimate the generate heat and associated thermal effect soon because of that also. – That means we’d better starting the thermal works to prevent it becoming a matter with violation of thermal

Unfortunately, we can’t find the appropriate information (thermal resistance, maximum junction temperature). Could you let us have these information soon not mentioned to help of circuit integration happened to an AP. It’s looked forward to getting your feedback soon

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( 2017-08-11 15:52:38 +0200 )editconvert to answer

Hi all, to recap my points, I need thermal information such like (1) maximum junction temperature (2) thermal resistance, Theta j-c, Theta j-b and Theta j-a to run thermal simulation for an AP. Could anyone help? Thanks

( 2017-08-11 16:10:36 +0200 )editconvert to answer

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I have never seen Nordic provide theta JC, JA, etc. data for the nRF products. They draw such low current that the junction temp rise relative to ambient will be rather small under any condition. You should be able to just follow their ambient temp guidelines in the product spec and not be concerned with the junction temp.

However, if you wish to be more thorough you can easily write some custom code to exercise the nRF per your products requirements and just measure the core temp using built in temp sensor and that will give you theta J-A.

See this answer where Nordic discusses this solution: https://devzone.nordicsemi.com/questi...

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It's a great reference for the earlier nRF51 series. Thanks.

( 2017-08-14 16:38:38 +0200 )editconvert to answer

Theta j-a highly depends on your board layout, and if it is 2, 4 or more layers.

I did not find anything for the AQFN73 package, but figures for regular QFN 7x7mm are in the 33-50°C/W range for Theta j-a.

But just looking at the current consumtion figures reval this as a non-issue. I strugge to get anything above 25mA consumtion for the entire chip, which yields less than 0.1W heat - or about 5 degress celsius over ambient.

Unless you do something crazy like shorting many output pins, the genereated heat will not be a problem.

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Thanks. It's a great comment. I shoud not concern too much when running thermal simulation if I target on the temperature of PCB less than 85C.

( 2017-08-14 16:37:01 +0200 )editconvert to answer

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