For most of isolated gate driver, the peak current is 4A. If this current is not large enough, how to increase this current?
One way of increasing the drive strength of the system is to reduce the external series resistor size, but this can only happen to a reasonable limit. The required size of the external series resistor needs to be large enough to provide adequate damping, so keeping the loop from the gate driver to the power device gate is important.
If the output drive strength of a gate driver needs to be increased further, an external buffer can be added. These can be in the form of a source follower totem pole made of discrete N and P devices, or as a module such as the ZXGD3002E6.
The 4A rating can be a misleading metric. Sometimes the peak current rating in the title of a datasheet is a short circuit current, and sometimes it is the intended current in application. These are two different things. In application, a gate driver almost always uses an external series gate resistor to help dampen the circuit, and provide power dissipation outside of the driver. When this happens, the actual peak current is less than a rated short circuit current (tested without resistor). The more telling metric is the Rdson of the the gate driver if the gate driver output stage is constructed of MOSFETs.
Thanks for your detail explanation. Another question is, how to supply ZXGD3002E6, do still use the same bootstrap circuitry for high side buffer?
Yes, you can use the same bootstrap circuitry. Strangely enough, the peak current is not what dictates how much power is needed to be supplied to the bootstrap cap. The power usage to charge and discharge the the gate is dictated by:
Qg x Vgate x Fs
The average current needed to drive the gate will be approximately the same with the booster stage (except for the extra quiescent current).
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