L6706 datasheet(39/47 Pages) STMICROELECTRONICS

39 / 47 page

L6706

Driver section

Doc ID 15698 Rev 2

39/47

Driver section

The integrated high-current driver allow using different types of power MOS (also multiple

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

The driver for the high-side MOSFETs use BOOT pin for supply and PHASE pin for return.

The driver for the low-side MOSFETs use VCCDR pin for supply and PGND pin for return. A

minimum voltage at VCCDR pin is required to start operations of the device.

The controller embodies a sophisticated anti-shoot-through system to minimize low side

body diode conduction time maintaining good efficiency saving the use of Schottky diodes:

when the high-side MOSFET turns off, the voltage on its source begins to fall; when the

voltage reaches 2 V, the low-side MOSFET gate drive is suddenly applied. When the low-

side MOSFET turns off, the voltage at LGATE pin is sensed. When it drops below 1V, the

high-side MOSFET gate drive is suddenly applied.

If the current flowing in the inductor is negative, the source of high-side MOSFET will never

drop. To allow the turning on of the low-side MOSFET even in this case, a watchdog

controller is enabled: if the source of the high-side MOSFET doesn't drop, the low side

MOSFET is switched on so allowing the negative current of the inductor to recirculate. This

mechanism allows the system to regulate even if the current is negative.

The BOOT and VCCDR pin are separated from IC's power supply (VCC pin) as well as

signal ground (SGND pin) and power ground (PGND pin) in order to maximize the switching

noise immunity.

L6706 Datasheet(PDF) 39 Page - STMicroelectronics