The gate drive current strength, IDRIVE, is selected based on the gate-to-drain charge of the external MOSFETs and the target rise and fall times at the switch-node. If IDRIVE is selected to be too low for a given MOSFET, then the MOSFET may not turn on or off completely within the configured tDRIVE time and a gate fault may be asserted. Additionally, slow rise and fall times will lead to higher switching power losses in the external power MOSFETs. It is recommended to verify these values in system with the required external MOSFETs and load to determine the optimal settings.
The IDRIVEP and IDRIVEN for both the high-side and low-side external MOSFETs are adjustable on SPI device variants. On hardware interface device variants, both source and sink settings are selected simultaneously on the IDRIVE pin.
For MOSFETs with a known gate-to-drain charge (QGD), desired rise time (trise), and a desired fall time (tfall), use Equation 3 and Equation 4 to calculate the approximate values of IDRIVEP and IDRIVEN (respectively).
Using the input design parameters as an example, we can calculate the approximate values for IDRIVEP and IDRIVEN.
Based on these calculations a value of 6 mA was chosen for IDRIVEP.
Based on these calculations, a value of 16 mA was chosen for IDRIVEN.