L6388ED datasheet(9/18 Pages) STMICROELECTRONICS

Part #	L6388ED

Description	High-voltage high and low side driver

PDF	18 Pages

Scroll/Zoom	100%

Manufacturer	STMICROELECTRONICS [STMicroelectronics]

Direct Link	http://www.st.com

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9 / 18 page

L6388E

Bootstrap driver

9/18

The following equation is useful to compute the drop on the bootstrap DMOS:

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 1V, if the Tcharge is 5µs. In fact:

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.

drop

arg Rdson

drop

→

gate

arg

-------------------R

dson

drop

30nC

µs

--------------- 125

Ω 0.8V

∼

⋅

L6388ED Datasheet(PDF) 9 Page - STMicroelectronics