DocID025240 Rev 2

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AN4355

Gate driving circuitry

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Both the high-side and low-side gate drivers are programmable current generators which

allow to charge and discharge the MOSFETs gate with a constant current. The gate drivers

also integrate a Miller clamp MOSFET which avoids induced turn-on effect.

The low-side gate driver is supplied by the VCC pin which can be connected both to an

external voltage source and to the integrated linear regulator which generates the supply

voltage (7.5 V or 15 V according to the configuration) from the VSREG supply pin.

The high-side gate driver is supplied by charge pump circuitry. This way the on time of the

high-side MOSFET is not limited as in the case of a bootstrap capacitor. A clamping diode

limits the gate-source voltage of the high-side MOSFET to 17 V avoiding the breaking of the

gate in case of the power stage output is short-circuited to ground. In fact in this case, if the

voltage limiter was not present, the final gate-source voltage of the high-side MOSFET was

Figure 11. high-side gate driver operation when output is shorted to ground

Warning:

breakdown, but not by the high current which can be

generated by the short-circuit condition.