switches - What is the purpose of "MOSFET driver" IC's

There are dedicated "MOSFET driver" IC's available (ICL7667, Max622/626, TD340, IXD*404). Some also control IGBTs. What is the practical purpose of these? Is it all about maximizing the switching speed (driving gate capacitance) or are there other motives?

Answer

A MOSFET driver IC (like the ICL7667 you mentioned) translates TTL Or CMOS logical signals, to a higher voltage and higher current, with the goal of rapidly and completely switching the gate of a MOSFET.

An output pin of a microcontroller is usually adequate to drive a small-signal logic level MOSFET, like a 2N7000. However, two issues occur when driving larger MOSFETs:

1. Higher gate capacitance - Digital signals are meant to drive small loads (on the order of 10-100pF). This is much less than the many MOSFETs, which can be in the thousands of pF.


2. Higher gate voltage - A 3.3V or 5V signal is often not enough. Usually 8-12V is required to fully turn on the MOSFET.

Finally, many MOSFET drivers are designed explicitly for the purpose of controlling a motor with an H-bridge.