L6717 datasheet(48/56 Pages) STMICROELECTRONICS

48 / 56 page

High current embedded drivers

L6717

48/56

Doc ID 17326 Rev 1

10.2

Power dissipation

It is important to consider the power that the device is going to dissipate in driving the exter-

nal MOSFETs in order to avoid overcoming the maximum junction operative temperature.

Two main terms contribute in the device power dissipation: bias power and drivers' power.

●

Device power (PDC) depends on the static consumption of the device through the

supply pins and it is simply quantifiable as follow:

●

Drivers' power is the power needed by the driver to continuously switch ON and OFF

the external MOSFETs; it is a function of the switching frequency and total gate charge

of the selected MOSFETs. It can be quantified considering that the total power PSW

dissipated to switch the MOSFETs 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 MOSFETs for each phase featuring embedded

driver results:

Where QGHSx is the total gate charge of the HS MOSFETs and QGLSx is the total gate

charge of the LS MOSFETs for both CORE and NB sections (only Phase1 and Phase2

for CORE section); VBOOTx is the driving voltage for the HSx MOSFETs.

VCCDR

⋅

SWx

GLSx

VCCDR

⋅

GHSx

VBOOTx

⋅

()

⋅

L6717 Datasheet(PDF) 48 Page - STMicroelectronics