AD7416: Ambient temperature and PCB temperature

Document created by analog-archivist Employee on Feb 23, 2016
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As an Reliability Engineer, I need a temperature model of the AD7416 internal
temp. sensor, which is coupled by an specific RTH to the PCB and by another to
the ambient cooling air. The reason is to know, which temperature is measure,
that of the PBC or the ambient air. The data sheet provides no information
about that. Thank you in advance.

 

Essentially the AD7416 and all pcb mounted temperature sensors will measure the
temperature of the PCB. The reason is that approx. 60%-70% of the heat transfer
is through the devices pins.
If customers want to measure the ambient air then we recommend that they place
the parts a good distance away from any potential pcb heat sources e.g.
uControllers.
We also recommend that GND and Vdd copper planes are kept away from the part as
they will conduct heat to the part. Small track traces to the part are
recommended.

If the customer wants to measure the pcb temperature then ideally he should
place the part on the main GND plane and depending on the size of the pcb,
place a few on different parts of the pcb.
Some customers use the GND plane as a heat sink so temperature close to a heat
source will be higher than temperature on the GND plane a good distance away
from the heat source.

In short, the AD7416 will track the temperature of the pcb in it's immediate
vicinity.

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