Question regarding DRV8305 and MOSFETs

Hi Dinesh,

In case you have not seen this, please refer to the Applicaton Report "Understanding IDRIVE and TDRIVE in TI Motor Gate Drivers" SLVA714.

Prior to IDRIVE and TDRIVE features, external gate resistance was needed to adjust the slew rate of the driver. In some cases, two paths were created. One was a resistor only and the other was a resistor/diode combination. This allowed one path to be faster than the other.

To your questions:

1) Is it good to put external gate resistance? please tell me the advantage and disadvantage of that external gate resistance.

What will be good design? With gate resistance or without gate resistance?

In general, it is good to have a footprint for external gate resistance. The resistor can be 0 Ohms with devices that have IDRIVE/TDRIVE. If there is a reason to further reduce the slew rate it can be done by changing the resistor.

The disadvantage is that dead time may have to be adjusted. In many devices, dead time begins when the driver detects the gate is off. The resistor can affect this time.

2) Second question is about the resistance between gate and source of the each MOSFET. Is it good to put a resistance between the gate and source? If it is good then please tell me the advantages of that.

What will be good design? With gate-source resistance or without it?

This is generally not recommended. When the FET is on, this is creating a static load on the driver. Is there a specific concern that you have?