L6598

Block diagram description

Doc ID 6554 Rev 7

13/24

5.3

Bootstrap section

The supply of the high voltage section is obtained by means of a bootstrap circuitry. This

solution normally requires an high voltage fast recovery diode for charging the bootstrap

capacitor (fig. 14a). In the device a patented integrated structure, replaces this external

diode. It is released by means of a high voltage DMOS, driven synchronously with the low

side driver (LVG), with in series a diode, as shown in fig. 14b.

Figure 13.

Bootstrap driver

To drive the synchronized DMOS it is necessary a voltage higher than the supply voltage

Vs. This voltage is obtained by means of an internal charge pump (fig. 14b).

The diode connected in series to the DMOS has been added to avoid undesirable turn on of

it. The introduction of the diode prevents any current can flow from the Vboot pin to the VS

one in case that the supply is quickly turned off when the internal capacitor of the pump is

not fully discharged.

Figure 12.