L6911E datasheet(13/34 Pages) STMICROELECTRONICS

13 / 34 page

L6911E

Device description

13/34

Figure 4.

Soft start

5.4

Driver section

The driver capability on the high and low side drivers allows to use different types of power

MOS (also multiple MOS to reduce the Rds(ON)), maintaining fast switching transition.

The low-side mos driver is supplied directly by Vcc while the high-side driver is supplied by

the BOOT pin.

Adaptative dead time control is implemented to prevent cross-conduction and allow to use

many kinds of mosfets. The upper mos turn-on is avoided if the lower gate is over about

200mV while the lower mos turn-on is avoided if the PHASE pin is over about 500mV. The

upper mos is in any case turned-on after 200nS from the low side turn-off.

The peak current is shown for both the upper (Figure 5 on page 14) and the lowr (Figure 6

on page 14) driver at 5V and 12V. a 4nF capacitive load has been used in these

measurements.

For the lower driver, the source peak current is 1.1A @ VCC = 12V and 500mA @ VCC = 5V,

and the sink peak current is 1.3A @ VCC = 12V and 500mA @ VCC = 5V.

Similary, for the upper driver, the source peak current is 1.3A @ Vboot-Vphase = 12V and

600mA @ Vboot-Vphase = 5V, and the sink peak current is 1.3A @ Vboot-Vphase = 12V

and 550mA @ Vboot-Vphase = 5V.

Vcc Turn-on threshold

Vin Turn-on threshold

0.5V

Vcc

Vin

Vss

LGATE

Vout

to GND

Timing diagram

CH3 = PGOOD; CH4 = VSS

Aquisition: CH1 = PHASE; CH2 = VOUT;

CH3 = PGOOD; CH4 = VSS

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