isl6333 Intersil Corporation, isl6333 Datasheet - Page 33

• Manufacturer Part Number: isl6333
• Description: Three-phase Buck Pwm Controller With Integrated Mosfet Drivers And Light Load Efficiency Enhancements For Intel Vr11.1 Applications
• Manufacturer: Intersil Corporation

The total gate drive power losses are dissipated among the
resistive components along the transition path and in the
bootstrap diode. The portion of the total power dissipated in
the controller itself is the power dissipated in the upper drive
path resistance, P
P
power will be dissipated by the external gate resistors (R
and R
the MOSFETs. Figures 20 and 21 show the typical upper and
lower gate drives turn-on transition path. The total power
dissipation in the controller itself, P
estimated as calculated in Equation 32:
P
P
P
R
P
DR_UP
FIGURE 21. TYPICAL LOWER-GATE DRIVE TURN-ON PATH
DR
DR_UP
DR_LOW
FIGURE 20. TYPICAL UPPER-GATE DRIVE TURN-ON PATH
EXT1
PVCC
BOOT
PVCC
=
G2
P
=
, and in the boot strap diode, P
) and the internal gate resistors (R
=
DR_UP
=
PHASE
R
=
P
---------------------
R
⎛
⎜
⎝
R
G1
LO2
Qg_Q1
--------------------------------------
R
BOOT
HI2
⎛
⎜
⎝
R
R
HI1
--------------------------------------
R
3
LO1
+
HI1
HI2
+
R
-------------
R
N
+
P
DR_UP
GI1
HI1
Q1
R
R
+
DR_LOW
HI2
EXT1
R
LGATE
EXT2
UGATE
, the lower drive path resistance,
+
+
--------------------------------------- -
R
+
33
LO1
--------------------------------------- -
R
P
R
LO2
BOOT
EXT2
R
R
G2
R
+
LO1
R
G
DR
G1
+
R
LO2
G
ISL6333, ISL6333A, ISL6333B, ISL6333C
EXT1
R
+
, can be roughly
=
R
C
EXT2
GI2
BOOT
(
GD
R
R
C
I
C
Q
GI1
GD
G2
GS
⎞ P
⎟
⎠
C
⋅
GI1
VCC
⋅
⎞ P
⎟
⎠
GS
+
. The rest of the
---------------------
⋅
S
Qg_Q1
---------------------
R
-------------
N
and R
Qg_Q2
GI2
S
3
Q2
)
2
D
D
GI2
Q
C
(EQ. 32)
2
DS
Q
C
) of
1
G1
DS
Inductor DCR Current Sensing Component
Selection
The controllers sense each individual channel’s inductor
current by detecting the voltage across the output inductor
DCR of that channel (As described in the “Continuous Current
Sensing” on page 21). As Figure 22 illustrates, an R-C
network is required to accurately sense the inductor DCR
voltage and convert this information into a current, which is
proportional to the total output current. The time constant of
this R-C network must match the time constant of the inductor
L/DCR.
Follow the steps below to choose the component values for
this RC network.
Once the R-C network components have been chosen, the
effective internal R
R
loop as well as the gain of the channel-current balance loop
and the overcurrent trip level. The effective internal R
resistance is set through a single resistor on the RSET pin,
R
Use Equation 34 to calculate the value of R
Equation 34, DCR is the DCR of the output inductor at room
temperature, I
N is the number of phases. It is recommended that the
R
1. Choose an arbitrary value for C
2. Plug the inductor L and DCR component values, and the
ISEN
SET
1
=
MOSFET
value is 0.1µF.
value for C
calculate the value for R
DRIVER
..
-------------------------
DCR C
resistance sets the gain of the load line regulation
FIGURE 22. DCR SENSING CONFIGURATION
SENSE
L
⋅
I
n
1
OCP
1
UGATE
LGATE
I
chosen in step 1, into Equation 33 to
SEN
ISEN
is the desired overcurrent trip level, and
ISL6333 INTERNAL
+
-
CIRCUIT
resistance must then be set. The
1
R
V
.
ISEN
C
(s)
-
1
R
INDUCTOR
. The recommended
1
L
V
ISEN-
ISEN+
RSET
L
I L
(s)
V
R
C
DCR
SET
SET
-
(s)
C
1
-
. In
April 10, 2008
VCC
C
(EQ. 33)
V
ISEN
OUT
FN6520.0
OUT