Gate drivers setup

AN4354

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DocID025239 Rev 2

Figure 9. Gate charge graph

2.2

Deadtime (TDT)

The deadtime is a period between the end of the turn-off of a MOSFET and the turn-on of

the opposite one. This time is required to avoid cross conduction effects. The deadtime

duration should be proportional with the commutation time: faster commutations usually

allow shorter deadtime.

In most cases a deadtime between 125 and 375 ns is enough for proper operation.

2.3

Blanking time (TBLANK)

At the end of each commutation the sensing circuitry is disabled during the blanking time.

The duration of the blanking time depends on the characteristics of the MOSFETs, in

particular the body diode, the layout of the application and the commutation speed. These

parameters generate the electrical perturbations which must be masked in order to avoid

spurious triggering of the sensing circuitry.

In most cases a blanking time between 375 and 750 ns is enough for proper operation. For

very fast commutation speed the maximum blanking time value should be used.

2.4

Wrong setup issues

When the gate driver setup is not properly set the system operation is compromised.

If the gate charge is lower than the total gate charge, the MOSFET is not completely turned

actual charge supplied by the gate drivers two different scenarios could occur.

In the first scenario the gate charge is enough to complete the Miller plateau region, but the

target value increasing the power dissipation and lowering the overcurrent threshold. In fact