E-L6598D013TR Datasheet, PDF (13/24 Pages) STMicroelectronics – High voltage resonant controller

L6598
Figure 12. Typ. (f_start-f_min) vs.
R_fstar @ C_f = 470 pF
Block diagram description
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.
Doc ID 6554 Rev 7
13/24