In this application example the device is configured for single supply operation. This configuration requires only one power supply for the DRV835x but comes at the tradeoff of increased internal power dissipation. 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, all 3 high-side and 3 low-side MOSFETs switching, and a switching frequency of 45 kHz.
Use Equation 26, Equation 27, Equation 28, Equation 29, and Equation 31 to calculate the value of Ptot for VVM = VVDRAIN = VVIN = 48 V, IVM = 9.5 mA, IVCP = 10.5 mA, IVGLS = 10.5 mA, VVCC = 3.3 V, IVCC = 100 mA, and η = 86 %.
Lastly, to estimate the device junction temperature during operation, use Equation 32 to calculate the value of TJmax for TAmax = 60°C, RθJA = 26.6°C/W for the RGZ package, and Ptot = 2.054 W. Again, please 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, see the Semiconductor and IC Package Thermal Metrics application report.
As shown in this example, the device is within its operational limits, but is operating almost to its maximum operational junction temperature. Design care should be taken in the single supply configuration to correctly manage the power dissipation of the device.