AN4043 datasheet(34/60 Pages) STMICROELECTRONICS

Part #	AN4043

Description	In recent years the variable speed motor control market has required high performance

PDF	60 Pages

Scroll/Zoom	100%

Manufacturer	STMICROELECTRONICS [STMicroelectronics]

Direct Link	http://www.st.com

Logo

34 / 60 page

Electrical characteristics and functions

AN4043

34/60

Doc ID 022726 Rev 2

Equation 12

where

δ is the duty cycle of the PWM signal and RDS(on) is 120 Ω typical value, as shown in

the datasheet.

A practical example can be done by considering a motor drive application where the PWM

switching frequency is 16 kHz, with a duty cycle of 50%, and

ΔVCBOOT = 0.1 V (that means,

a gate driver supply voltage VCC = 17.5 V). From the graph in Figure 21 the bootstrap

capacitance is 1.0 µF, therefore the CBOOT can be selected by using a value between 2.0

and 3.0 µF. According to the commercial value the bootstrap capacitor can be 2.2 µF. From

Equation 12Equation 12, the initial charging time is:

Equation 13

For safety reasons, the initial charging time must be at least 8.1 ms.

⎟⎟

⎠

⎞

⎜⎜

⎝

⎛

⋅

≥

CBOOT

)

(

BOOT

CHA RGE

120

CHARGE

⎟⎟⎠

⎞

⎜⎜⎝

⎛

⋅

≥

−

AN4043 Datasheet(PDF) 34 Page - STMicroelectronics