AN4671

Gate driver specs and implementation

DocID027654 Rev 1

13/17

3

Gate driver specs and implementation

The following is a short list of the minimum gate driving requirements:

1.

Dv/dt transient immunity: ±50 V/ns across the entire temperature range

SiC MOSFETs are tailored to switch fast and operate at high frequencies, hence the

intrinsic device dv/dt is higher than that observed on silicon IGBTs.

2.

Minimum differential supply voltage swing: 22-28 V

SiC MOSFETs require a higher positive gate drive voltage (+20 V) and, depending on

the application, a negative OFF gate voltage in the -2 V to -6 V range. The maximum

supply voltage rating of the driver must be between 22 V and 28 V depending on

whether a negative OFF voltage is applied. Given that the gate charge required to

switch the device is low, the higher voltage swing doesn’t affect the required gate drive

power.

3.

The current capability (sink/source current) to drive the 1200 V,100

mΩ SCT30N120 is

2 A minimum across all temperatures

It is required to enable the lowest achievable switching losses as the waveforms

reported in the previous paragraph clearly show that the gate peak current is close to

2 A at maximum switching speeds (external gate resistor = 1

Ω).

The ideal SiC MOSFET gate driver therefore represents a ‘black box’ that enables the full

potential of the device. It must therefore drive the gate with a higher voltage swing and

larger current capability than common IGBT drivers.

The STGAP1S gapDRIVE™ is the preferred ST option to drive SiC MOSFETs among the

several ST solutions available: it is a galvanically isolated single gate driver with advanced

protection, configuration and diagnostic features for N-channel MOSFETs and IGBTs.

Figure 13: STGAP1S block diagram