Moteur de recherche de fiches techniques de composants électroniques
  French  ▼

Delete All
ON OFF
ALLDATASHEET.FR

X  

Preview PDF Download HTML

ISL6566 Fiches technique(PDF) 20 Page - Intersil Corporation

No de pièce ISL6566
Description  Three-Phase Buck PWM Controller with Integrated MOSFET Drivers for VRM9, VRM10, and AMD Hammer Applications
Download  28 Pages
Scroll/Zoom Zoom In 100%  Zoom Out
Fabricant  INTERSIL [Intersil Corporation]
Site Internet  http://www.intersil.com/cda/home
Logo INTERSIL - Intersil Corporation

ISL6566 Fiches technique(HTML) 20 Page - Intersil Corporation

Back Button ISL6566 Datasheet HTML 16Page - Intersil Corporation ISL6566 Datasheet HTML 17Page - Intersil Corporation ISL6566 Datasheet HTML 18Page - Intersil Corporation ISL6566 Datasheet HTML 19Page - Intersil Corporation ISL6566 Datasheet HTML 20Page - Intersil Corporation ISL6566 Datasheet HTML 21Page - Intersil Corporation ISL6566 Datasheet HTML 22Page - Intersil Corporation ISL6566 Datasheet HTML 23Page - Intersil Corporation ISL6566 Datasheet HTML 24Page - Intersil Corporation Next Button
Zoom Inzoom in Zoom Outzoom out
 20 / 28 page
background image
20
FN9178.3
July 25, 2005
UPPER MOSFET POWER CALCULATION
In addition to rDS(ON) losses, a large portion of the upper-
MOSFET losses are due to currents conducted across the
input voltage (VIN) during switching. Since a substantially
higher portion of the upper-MOSFET losses are dependent
on switching frequency, the power calculation is more
complex. Upper MOSFET losses can be divided into
separate components involving the upper-MOSFET
switching times, the lower-MOSFET body-diode reverse-
recovery charge, Qrr, and the upper MOSFET rDS(ON)
conduction loss.
When the upper MOSFET turns off, the lower MOSFET does
not conduct any portion of the inductor current until the
voltage at the phase node falls below ground. Once the
lower MOSFET begins conducting, the current in the upper
MOSFET falls to zero as the current in the lower MOSFET
ramps up to assume the full inductor current. In Equation 17,
the required time for this commutation is t1 and the
approximated associated power loss is PUP,1.
At turn on, the upper MOSFET begins to conduct and this
transition occurs over a time t2. In Equation 18, the
approximate power loss is PUP,2.
A third component involves the lower MOSFET reverse-
recovery charge, Qrr. Since the inductor current has fully
commutated to the upper MOSFET before the lower-
MOSFET body diode can recover all of Qrr, it is conducted
through the upper MOSFET across VIN. The power
dissipated as a result is PUP,3.
Finally, the resistive part of the upper MOSFET is given in
Equation 20 as PUP,4.
The total power dissipated by the upper MOSFET at full load
can now be approximated as the summation of the results
from Equations 17, 18, 19 and 20. Since the power
equations depend on MOSFET parameters, choosing the
correct MOSFETs can be an iterative process involving
repetitive solutions to the loss equations for different
MOSFETs and different switching frequencies.
Package Power Dissipation
When choosing MOSFETs it is important to consider the
amount of power being dissipated in the integrated drivers
located in the controller. Since there are a total of three
drivers in the controller package, the total power dissipated
by all three drivers must be less than the maximum
allowable power dissipation for the QFN package.
Calculating the power dissipation in the drivers for a desired
application is critical to ensure safe operation. Exceeding the
maximum allowable power dissipation level will push the IC
beyond the maximum recommended operating junction
temperature of 125°C. The maximum allowable IC power
dissipation for the 6x6 QFN package is approximately 4W at
room temperature. See Layout Considerations paragraph for
thermal transfer improvement suggestions.
When designing the ISL6566 into an application, it is
recommended that the following calculation is used to
ensure safe operation at the desired frequency for the
selected MOSFETs. The total gate drive power losses,
PQg_TOT, due to the gate charge of MOSFETs and the
integrated driver’s internal circuitry and their corresponding
average driver current can be estimated with Equations 21
and 22, respectively.
In Equations 21 and 22, PQg_Q1 is the total upper gate drive
power loss and PQg_Q2 is the total lower gate drive power
loss; the gate charge (QG1 and QG2) is defined at the
particular gate to source drive voltage PVCC in the
corresponding MOSFET data sheet; IQ is the driver total
quiescent current with no load at both drive outputs; NQ1
and NQ2 are the number of upper and lower MOSFETs per
phase, respectively; NPHASE is the number of active
phases. The IQ*VCC product is the quiescent power of the
controller without capacitive load and is typically 75mW at
300kHz.
PUP 1, VIN
IM
N
------
IPP
2
---------
+

 t1
2
----



fS
(EQ. 17)
PUP 2
,
VIN
IM
N
------
IPP
2
---------

 t2
2
----



fS
(EQ. 18)
PUP 2
,
VIN
IM
N
------
IPP
2
---------

 t2
2
----



fS
PUP 3,
VIN Qrr fS
=
(EQ. 19)
PUP 4, rDS ON
()
IM
N
------


 2
d
IPP
2
12
----------
+
(EQ. 20)
FIGURE 15. TYPICAL UPPER-GATE DRIVE TURN-ON PATH
PQg_TOT
PQg_Q1 PQg_Q2 IQ VCC
++
=
(EQ. 21)
PQg_Q1
3
2
--- QG1 PVCC
FSW
NQ1
NPHASE
=
PQg_Q2
QG2 PVCC
FSW
NQ2 NPHASE
=
IDR
3
2
--- QG1 N
Q1
QG2 NQ2
+

 N
PHASE
FSW IQ
+
=
(EQ. 22)
Q1
D
S
G
RGI1
RG1
BOOT
RHI1
CDS
CGS
CGD
RLO1
PHASE
PVCC
UGATE
ISL6566


Html Pages

1  2  3  4  5  6  7  8  9  10  11  12  13  14  15  16  17  18  19  20  21  22  23  24  25  26  27  28 


Fiches technique Télécharger

Go To PDF Page


Lien URL




Politique de confidentialité
ALLDATASHEET.FR
ALLDATASHEET vous a-t-il été utile ?  [ DONATE ] 

À propos de Alldatasheet   |   Publicité   |   Contactez-nous   |   Politique de confidentialité   |   Echange de liens   |   Fabricants
All Rights Reserved©Alldatasheet.com


Mirror Sites
English : Alldatasheet.com  |   English : Alldatasheet.net  |   Chinese : Alldatasheetcn.com  |   German : Alldatasheetde.com  |   Japanese : Alldatasheet.jp
Russian : Alldatasheetru.com  |   Korean : Alldatasheet.co.kr  |   Spanish : Alldatasheet.es  |   French : Alldatasheet.fr  |   Italian : Alldatasheetit.com
Portuguese : Alldatasheetpt.com  |   Polish : Alldatasheet.pl  |   Vietnamese : Alldatasheet.vn