L6747A STMicroelectronics, L6747A Datasheet - Page 12

• Manufacturer Part Number: L6747A
• Description: High current MOSFET driver
• Manufacturer: STMicroelectronics

Specifications of L6747A

• Flexible Gate-drive: 5 V to 12 V compatible

Device description and operation
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Traces between the driver and the MOSFETS should be short and wide to minimize the
inductance of the trace, which in turn minimizes ringing in the driving signals. Moreover, the
VIA count should be minimized to reduce the related parasitic effect.
The use of a 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. Place the bypass capacitor
(VCC, PVCC and BOOT capacitors) close to the device with the shortest possible loop,
using wide copper traces to minimize parasitic inductance.
Systems that do not use Schottky diodes in parallel with the low-side MOSFET might show
large negative spikes on the PHASE pin. This spike can be limited, as can the positive spike,
but has an additional consequence: it causes the bootstrap capacitor to be overcharged.
This extra charge can cause, in the worst case condition of maximum input voltage and
during particular transients, that boot-to-phase voltage exceeds the absolute maximum
ratings causing device failures. It is therefore suggested in this cases to limit this extra
charge by adding a small R
also contributes in the limitation of the spike present on the BOOT pin.
For heat dissipation, place the copper area under the IC. This copper area may be
connected by internal copper layers through several VIAs to improve thermal conductivity.
The combination of copper pad, copper plane and VIAs under the driver allows the device to
achieve its best thermal performance.
Figure 7.
Figure 8.
LS DRIVER
LGATE
C
GND
VCC
BOOT
R
BOOT
Driver turn-on and turn-off paths
External component placement example
R
GATE
LS MOSFET
R
BOOT
INT
PWM
C
VCC
BOOT
GS
C
EN
GD
Doc ID 17126 Rev 1
resistor in series with the boot capacitor. The use of R
C
Rboot
1
2
3
4
C
DS
Cboot
8
7
6
5
HS DRIVER
UGATE
PHASE
GND
LGATE
HGATE
PHASE
BOOT
C
VCC
BOOT
R
BOOT
R
GATE
HS MOSFET
R
INT
C
GS
C
GD
L6747A
BOOT
C
DS