L6398 datasheet(12/16 Pages) STMICROELECTRONICS

Part #	L6398

Description	High voltage high and low side driver

PDF	16 Pages

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Manufacturer	STMICROELECTRONICS [STMicroelectronics]

Direct Link	http://www.st.com

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12 / 16 page

Bootstrap driver

L6398

12/16

Doc ID 18199 Rev 3

where Qgate is the gate charge of the external power MOS, Rdson is the on resistance of the

bootstrap DMOS and Tcharge is the charging time of the bootstrap capacitor.

For example: using a power MOS with a total gate charge of 30nC the drop on the bootstrap

DMOS is about 1 V, if the Tcharge is 5 μs. In fact:

Equation 4

Vdrop has to be taken into account when the voltage drop on CBOOT is calculated: if this drop

is too high, or the circuit topology doesn’t allow a sufficient charging time, an external diode

can be used.

Figure 6.

Bootstrap driver with high voltage fast recovery diode

Figure 7.

Bootstrap driver with internal charge pump

drop

30nC

μs

--------------- 120

Ω 0.7V

∼

⋅

TO LOAD

H.V.

HVG

LVG

CBOOT

DBOOT

BOOT

OUT

HVG

LVG

TO LOAD

H.V.

CBOOT

OUT

BOOT

L6398 Datasheet(PDF) 12 Page - STMicroelectronics