5.8 IC Drive Current and MOSFET/IGBT Gate Charge

Gate driver ICs are defined by their output drive current, its ability to source current to the gate of the MOSFET/IGBT at turn ON and to sink current from the gate of the MOSFET/IGBT at turn OFF. For the MCP14H2304, the drive current is source I_O+ = 290 mA typical, and sink I_O− = 600 mA, typical.

For a given MOSFET/IGBT, with the known drive current of the MCP14H2304, you can estimate how long it will take to turn on/off the MOSFET/IGBT with the equation:

$t=\frac{Q_g}{I}$

Where:

• Q_g is the total charge of the MOSFET/IGBT as provided by the datasheet
• I is the sink/source capability of the gate driver IC
• t is the calculated rise/fall time with the given charge and drive current

For example with the Diodes’ DGTD65T15H2TF, 650V IGBT, Q_g = 61 nC; and with the MCP14H2304 I_O+ = 290 nA and I_O− = 600 mA, the t_r = 210 ns and t_f = 102 ns. These are estimates, as the total charge given in the datasheet may not be the same conditions in the application. Also, the addition of a gate resistor will increase the t_r and t_f.