# Component Temperature Rise Example

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Figure 1: Surface Mount Inductor (Size = 0603).

I often have to model the rise of passive component temperatures with respect to some circuit parameter, like current or voltage. I thought I would present here a typical example of how the temperature of a passive part varies with current. In this case, I am feeding a constant current into the coil and I need to know what temperature rise I should expect with this component. I usually model component temperatures using two curves: a linear curve for low current levels, and a quadratic curve for high current levels. This model has worked reasonably well over the years.

Table 1 shows the raw data, which was taken by the coil manufacturer.

Table 1: Temperature Rise Versus Ambient Versus Current.

 IDC (mA) Rise Temp (°C) 10 0.4 20 0.7 50 0.9 100 1.2 200 2.3 500 11.5 600 16.5

Figure 2 shows a plot of Table 1 and how I model this data mathematically using two curves.

Figure 2: Inductor Temperature Rise with Current.

The size of the linear and quadratic regions varies with the type of part. You can see the same sort of thing with a lead-acid battery (example).

I generally divide the temperature rise characteristics into two regions:

• linear region

At low current levels, there is so little self-heating that the component's internal resistance of the device is not significantly affected by the self-heating. This means the component is behaving as a linear device (i.e. temperature rise that is proportional to current).