Device description and operation

L6743D

12/16

The use of multi-layer printed circuit board is recommended.

Small signal components and connections to critical nodes of the application as well as

bypass capacitors for the device supply are also important. Locate the bypass capacitor

(VCC, PVCC and BOOT capacitors) close to the device with the shortest possible loop and

use wide copper traces to minimize parasitic inductance.

Systems that do not use Schottky diodes in parallel to the low-side MOSFET might show big

negative spikes on the phase pin. This spike can be limited as well as the positive spike but

has an additional consequence: it causes the bootstrap capacitor to be over-charged. This

extra-charge can cause, in the worst case condition of maximum input voltage and during

particular transients, that boot-to-phase voltage overcomes the abs.max.ratings also

causing device failures. It is then suggested in this cases to limit this extra-charge by adding

the limitation of the spike present on the BOOT pin.

For heat dissipation, place copper area under the IC. This copper area may be connected

with internal copper layers through several VIAs to improve the thermal conductivity. The

combination of copper pad, copper plane and VIAs under the driver allows the device to

reach its best thermal performances.

Figure 7.

Driver turn-on and turn-off paths

Figure 8.

External components placement example

VCC

LS DRIVER

LS MOSFET

GND

LGATE

BOOT

HS DRIVER

HS MOSFET

PHASE

HGATE

VCC

Rboot

Cboot

1

2

3

4

LGATE

GND

PHASE

UGATE

VCC

EN

PWM

BOOT

5

6

7

8

L6743D