AM2908

Motor Driver ICs

AMtek semiconductors

July. 2020 V0.2

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Step 1 : Used the simulated Ψjt value listed above.

Step 2 : Measure Tt value by using

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Thermocouple Method

We recommend use of a small ~40 gauge(3.15mil diameter) thermocouple. The bead and

thermocouples wires should touch the top of the package and be covered with a minimal amount of

thermally conductive epoxy. The wires should be heat-insulated to prevent cooling of the bead due

to heat loss into wires. This is important towards preventing “too cool” Tt measurements, which

would lead to the calculated Tj also being too cool.



IR Spot Method

An IR Spot method should be utilized only when using a tool with a small enough spot area to

acquire the true top center “hot spot”.

Many so-called “small spot size” tools still have a measurement area of 0~100+mils at “zero”

distance of the tool from the surface. This spot area is too big for many smaller packages and likely

would result in cooler readings than the small thermocouple method. Consequently, to match

between spot area and package surface size is important while measuring Tt with IR sport method.

Step 3 : calculating power dissipation by

Step 4 : Estimate Tj value by

Tj= Ψjt x P+Tt

Step 5 : Calculated Θja value of actual PCB by the known Tj

Θja(actual) = (Tj-Ta)/P