AN487 APPLICATION NOTE

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Figure 24. Reset and power fail waveforms.

THE POWER STAGE

A simplified schematic of the output stage along with the external filter components is shown in fig.25.

Power stage and associated driving circuits are among the most critical components to achieve good per-

formances at high switching frequency. An external bootstrap capacitance, charged via diode D1 at 12V,

is needed to provide the correct gate drive to the power DMOS N-channel transistor. The driving circuit is

able to deliver a current peak of 0.5A, during turn on and turn off phases, to the gate of power DMOS tran-

sistor. The circuit-described shows commutation times of 50ns.

Figure 25. Power stage circuit.

The five devices of L497X family differentiate each other only for the level of current protection, while the

control part is the same and power device area is the same to guarantee low power dissipation also for

low current versions in DIP package.

Table 1 and fig. 26 shows electrical characteristics of the power DMOS implemented in the chip.