8.3.1.4.1 IDRIVE: MOSFET Slew-Rate Control

The IDRIVE component implements adjustable gate-drive current to control the MOSFET V_DS slew rates. The MOSFET V_DS slew rates are a critical factor for optimizing radiated emissions, energy and duration of diode recovery spikes, dV/dt gate turnon leading to shoot-through, and switching voltage transients related to parasitics in the external half-bridge. IDRIVE operates on the principal that the MOSFET V_DS slew rates are predominately determined by the rate of gate charge (or gate current) delivered during the MOSFET Q_GD or Miller charging region. By allowing the gate driver to adjust the gate current, it can effectively control the slew rate of the external power MOSFETs.

IDRIVE allows the DRV835x family of devices to dynamically switch between gate drive currents either through a register setting on SPI devices or the IDRIVE pin on hardware interface devices. The SPI devices provide 16 I_DRIVE settings ranging between 50-mA to 1-A source and 100-mA to 2-A sink. Hardware interface devices provides 7 I_DRIVE settings between the same ranges. The gate drive current setting is delivered to the gate during the turnon and turnoff of the external power MOSFET for the t_DRIVE duration. After the MOSFET turnon or turnoff, the gate driver switches to a smaller hold I_HOLD current to improve the gate driver efficiency. Additional details on the IDRIVE settings are described in the Register Maps section for the SPI devices and in the Pin Diagrams section for the hardware interface devices.