In high ambient operating environments, it may be important to estimate the internal self heating of the driver. To determine the temperature of the device, first the internal power dissipation must be calculate. After this an estimate can be made with the device package thermal properties.
The internal power dissipation has four primary components.
The values for PHS and PLS can be approximated by referencing the earlier equation for charge pump load current as shown below. In a typical switch scenario, 4 high-side and 4 low-side MOSFET are switching.
Using the input design parameters as an example, we can calculate the current load from the high-side and low-side drivers.
From this, the power dissipation can be calculated from the equations below for the driver power dissipation. The high-side and low-side includes a doubling factor to account for the losses in the charge pump supplying the drivers.
Using the input design parameters as an example, we can calculate the power dissipation from the high-side and low-side drivers.
Using the input design parameters as an example, we can calculate the power dissipation for the power supplies.
Finally, use Equation 30 to estimate device junction temperature.
Using the previously calculated power dissipation values and the device thermal parameter from the Section 7.4 table can estimate the device internal temperature: