L6714 STMicroelectronics, L6714 Datasheet - Page 30

• Manufacturer Part Number: L6714
• Description: IC CTRLR 4PH W/DRIVERS 64-TQFP
• Manufacturer: STMicroelectronics

Specifications of L6714

• Applications: Controller, Intel VR10, VR11, AMD CPU
• Voltage - Input: 12V
• Number Of Outputs: 4
• Voltage - Output: 0.3 ~ 1.6 V
• Operating Temperature: 0°C ~ 70°C
• Mounting Type: Surface Mount
• Package / Case: 64-TQFP Exposed Pad, 64-eTQFP, 64-HTQFP, 64-VQFP
• Mounting Style: SMD/SMT
• Case: QFP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Power dissipation
9
30/70
Power dissipation
L6714 embeds high current MOSFET drivers for both high side and low side MOSFET: it is
then important to consider the power the device is going to dissipate in driving them in order
to avoid overcoming the maximum junction operative temperature. In addition, since the
device has an exposed pad to better dissipate the power, the thermal resistance between
junction and ambient consequent to the layout is also important: thermal pad need to be
soldered to the PCB ground plane through several VIAs in order to facilitate the heat
dissipation.
Two main terms contribute to the device power dissipation: bias power and drivers' power.
The first one (P
and is simply quantifiable as follows (assuming to supply HS and LS drivers with the same
VCC of the device):
where N is the number of phases.
Drivers' power is the power needed by the driver to continuously switch on and off the
external MOSFET; it is a function of the switching frequency and total gate charge of the
selected MOSFET. It can be quantified considering that the total power P
switch the MOSFET (easy calculable) is dissipated by three main factors: external gate
resistance (when present), intrinsic MOSFET resistance and intrinsic driver resistance. This
last term is the important one to be determined to calculate the device power dissipation.
The total power dissipated to switch the MOSFET results:
External gate resistors help the device to dissipate the switching power since the same
power P
resulting in a general cooling of the device. When driving multiple MOSFET in parallel, it is
suggested to use one gate resistor for each MOSFET.
SW
will be shared between the internal driver impedance and the external resistor
DC
) depends on the static consumption of the device through the supply pins
P
SW
P
=
DC
N
=
F
V
SW
CC
Q
I
CC
GHS
+
N
V
BOOT
I
CCDRx
+
Q
+
GLS
N
I
BOOTx
V
CCDRx
SW
dissipated to
L6714