In this application example the device is configured for dual supply operation. dual supply operation helps to decrease the internal power dissipation by providing the gate driver with a lower supply voltage. This can be derived from the internal buck regulator or an external power supply. The junction temperature is estimated in the example below.
Use Equation 11 to calculate the value of IVCP and IVGLS for a MOSFET gate charge of 78 nC, 1 high-side and 1 low-side MOSFETs switch at a time, and a switching frequency of 20 kHz.
Use equation Equation 45, Equation 46, Equation 47, Equation 48, and Equation 50 to calculate the value of Ptot for VVM = 12 V, VVDRAIN = 48 V, VVIN = 48 V, IVM = 9.5 mA, IVCP = 1.56 mA, IVGLS = 1.56 mA, VVCC = 12 V, IVCC = 150 mA, and η = 86 %.
Lastly, to estimate the device junction temperature during operation, use Equation 51 to calculate the value of TJmax for TAmax = 105°C, RθJA = 26.6°C/W for the RGZ package, and Ptot = 0.51 W. Again, note that the RθJA is highly dependent on the PCB design used in the actual application and should be verified. For more information about traditional and new thermal metrics, refer to the Semiconductor and IC Package Thermal Metrics application report.